Compression and Backup - agree
File compression is a method of reducing the size of a file without a significant loss of information in order to save storage space and easy transfer of the files. Database compression is a method of reorganizing data to save space and increase performance. It could be a file or database, compression generally is meant to compress the size and speed up the file transfer.
There are two main types of compression namely; Lossy and lossless compression. This blog will provide insight into file and database compression with a short summary of the compression algorithms.
Lossy Compression
Lossy compression removes insignificant information and commonly done on video and audio files to reduce the file size. The loss is usually not noticeable, however, if the file is heavily compressed, then there would be a noticeable drop in quality.
This compression is a great option for image or video uploads, because it preserves the required information and reduces the file size but makes it easier for transfer and the loss in quality is usually not very noticeable to the user. This means Lossy compression reduces the quality of the media, but it is not visible to naked eye. The picture below is a simple example of how a PNG file is compressed to a JPEG file. While the size is reduced, there is not much of a visible effect from the output.
Lossy compression is not ideal for files where the details of the information are crucial (like in spreadsheets and word documents) because the compression can mess up the output; meaning when the file is decompressed the text might be garbled leading to loss of information.
Lossless Compression
Lossless compression reduces the file size without losing any information. The algorithm works on the principle of eliminating or handling redundancy. It can be applied to both text and image files. As there is no loss of information, when the file is decompressed, it will restore it to its original state.
This is a perfect technique for text compression where there is no compromise for loss of any data after decompression. Zip file program in Windows uses this method of compression.
Database Compression
Compression for databases can be done using lossy or lossless technique as well. The type of compression to be applied is decided based on the data stored in the database but most database applications use lossless compression to preserve the quality of data. Database applications employ different types of compression algorithms like run-length encoding, prefix encoding, compression using clustering, sparse matrices, dictionary encoding or any own proprietary compression methods.
Popular Compression Algorithms
Run-Length Encoding (RLE)
Run-Length Encoding is a lossless compression technique which scans data sequentially for repetitive value and its occurrence then encodes to a sequence of value and its count.
Example: WWWWHHHHYYYY
With RLE algorithm applied to the above line, it will be encoded to the following: 4W4H4Y
Prefix Encoding
This algorithm also removes redundant data but its rather difficult to implement. This compression technique uses prefix encoding to compress and then transfer the data.
Example
In the example above the data has the same prefix thus it was simple to choose the prefix, however usually data The problem with this compression is selecting the right prefix for data without much of similarity. This compression algorithm is good for date and time, and geolocation as these data have a good prefix pattern.
Dictionary Compression
Dictionary compression algorithms replace long strings with shorter codewords. The codewords are compiled into a dictionary and stored in the header row. As an example, let’s say a dictionary has codeword value as 1-life, 2-great, 3-and, 4-but. Now if the file content is “Life is great and fun but complicated”. These words will be replaced with indexes from the dictionary. Now the file will have 1is23fun4complicated. Use the dictionary to decompress the file to its original form. If the file has many words matching the values in the dictionary, then there will be a significant reduction in the file size.
Benefits of Database Compression
- Compression is used to reduce the overall database size to save database storage space. The compression rate is better if there is a lot of repetition in data values or there are many tables with less data or zero value data.
- Read speed is faster when the file size is small, however, the write operation might be a little slower because the data needs to be decompressed before the write operation.
- Resource utilization is lesser because more data can fit in memory or buffer.
Disadvantages of Database Compression
- Compression algorithms always build a keyword dictionary which is a part of the compressed database. If the database is small, there is a possibility that with the keyword dictionary the file size is larger than the original database.
- Extra overhead cost with compression and decompression because of extra CPU/ memory utilization.
- It is not recommended to compress numerical data and non-repetitive strings as this might increase or decrease the file size.
File Compression vs Database Compression
File data compression looks at how to minimize the value of the data items to reduce the size. Database compression, on the other hand, is an aggregate compression because it compresses data, indices, views, clusters and heaps. The compression is done on data across rows, columns, and at field level. BLOB data such as Image, video, and audio stored in the database can be compressed using the lossy compression.
Conclusion
In summary, compression is a technique to reduce the size of the file or database. This is very useful to reduce resource utilisation as well as save storage costs. A smaller size file or database is easy to transfer and speed operation processing. Not only this, a smaller file requires less memory and CPU utilization which is also another means to save overhead cost and increase data processing power. Large scale applications like Facebook, Google, or Oracle uses high-end compression algorithms like ZStandard, Snappy, XPress, and Oracle Advanced Compression to perform compression for the large data sets.
: LZ4 r Out of the three compression algorithms that are supported, this is the most efficient one, typically taking the shortest backup and restore times with the lowest CPU cost. See lz4—Extremely Fast Compression algorithm for more details, including a comparison with other compression algorithms.
: LZMA Out of the three supported compression algorithms, this typically provides the highest compression ratio; but it is also far more expensive in terms of CPU cost than the other two options. Thus we do not recommend this for active systems, but only for off-hour or inactive databases, or where I/O rates are extremely low.
: (For MySQL Enterprise Backup and later) Enables support for transparent page compression for InnoDB tables for directory backups, which means that when the target platform for the mysqlbackup backup or restore operation supports hole punching, mysqlbackup keeps the punched holes in the page-compressed InnoDB files it transfers.
Limitations: The feature is NOT supported in the following cases, for which punched holes are removed from the InnoDB files:
For single-file backups.
For TTS, incremental, compressed, or encrypted backups.
When a backup is not created in a file system (for example, when cloud storage is used to save the backup), or when the file system does not support sparse files.
For those pages of InnoDB data files that are modified by the redo log in an operation.
When the feature is enabled but hole punching fails, mysqlbackup issues a warning message after the operation is completed; for example:
Or:
A backup can be taken with and then be restored later without using the feature; the reverse is also true: a backup taken without using can be restored later with the feature.
Compression and Backup
In transferring data from synchrotrons, compressing files is essentialto reduce space and speed up transfers. In many cases on the home disks, much space can be saved if you compress some of your larger or infrequently used files. (Deleting temporary files etc will also help).Compressing Files
With compress, compressed files have a .Z extension: compress *img - compress all files matching pattern uncompress *img.Z - uncompresses all files with .Z extension With gzip, compressed files have a .gz extension gzip *img - gzip all files matching pattern gunzip *bilin.com.mx - gunzip all those files With bzip2, compressed files have a .bz2 extension bzip2 *img - bzip2 all files matching pattern bunzip2 *bilin.com.mx2 - bunzip2 all those filesFinding large or old files
If you're running out of space on your home disk, a sensible approach is to compress files that you don't use often. The biggest gain is made when applying this to large files. In order to find those files, use the findcommand: find ~ -size + -print which prints (-print) the names of all files from your home directory (~) on down that are greater (+) than blocks. If you omit the + it only prints files that are blocks, and that's of less use. The command: find ~ -mtime + -print prints the names of all files that were modified at least days ago. You can combine these features: find ~ -size + -mtime + -print which prints only large (> blocks), old (> 1 year) files. To compress these files using gzip, use: find ~ -size + -type f -mtime + -print -exec gzip '{}' \; gzip will whine if some of the files selected are already gzipped, so you can use more elaborate find syntax (-not -name '*.gz') if you like, or just ignore the error messages. I include "-type f" in the above command just to stop gzip even trying to compress links or directories - it won't but it will reduce potential error messages. Consult the manual page to find for more interesting options and features - really a very powerful program.Which compression program?
The old Unix compression program was compressis reasonably efficient but does no error checking. The newer Free Software Foundation program gzipis more efficient, does error checking and is widely available for all Unixes. An even newer program bzip2is a slower than gzip but does an even tighter job of compressing. It's available on Linux, OS X and I have installed it on our SGIs. I most frequently use gzip, but for situations where disk space is at a premium, bzip2 is probably better unless you are short on CPU.Here's a comparison of compression efficiencies and times on NINE data frames from X9A. This is in Linux on a local SCSI disk, timings averaged over three operations, default program options:
| Program | Time Taken | Final Size | Fraction of original size |
|---|---|---|---|
| compress | sec | ||
| gzip | sec | ||
| bzip2 | sec |
Actual compressed sizes depend on the strength of the data. However note that bzip2 is much more efficient at compression on these files at the cost of a whole lot of CPU. For decompression of these same frames (less of an issue):
| Program | Time Taken |
|---|---|
| uncompress | sec |
| gunzip | sec |
| bunzip2 | sec |
Note that for ASCII files (e.g. PDB files) often much greater compression efficiencies can be achieved. Gzip or bzip2 are always preferable to compress because of their error checking of the archive.
Testing archive integrity
If you are feeling sufficiently paranoid, or you suspect that data transfer may not be correct, you can test integrity of compressed frames by some variant on the following, which takes all .gz files in the current directory and reads them, disposing of the output. Error messages (e.g. corrupted files) are echo'd to the terminal. find . -name '*gz' -print -exec zcat '{}' \; > /dev/null zcat should be replaced by gzcat on the SGI.Note that very recent experience with older machines is that they can sometimes silently fail on writing files that they should otherwise have no problem with. It's not clear how this happens, but it certainly happened at APS beamlime 8BM. It may also have happened with xtreme4 locally.
Backup Options
We have a variety of drives within the floor: DDS-1 tape drive (SGI - currently Xtreme4), DDS-4 tape drive in Nikolov lab, Exabyte c tape drive (Ximpact1 - now unplugged), CD-RW (most Macs) and DVD-R (Facility G4, some Linux workstations, some Macs). The advantages of tape are their generally larger capacities. The advantages of optical media is that they are random access - you can read the last file off the CD-R quickly, whereas you have the read the entire tapeto get to the last file. Tapes are inherently re-usable. CD-R and DVD-R are not, and even their -RW versions have limited overwrite counts.| Media | Capacity | Notes |
|---|---|---|
| DDS-1 4mm DAT tape | Gb | Obsolete - drives no longer made |
| DDS-4 4mm DAT tape | Gb | Drives cannot read DDS-1 ? |
| Exabyte c 8mm tape | Gb | Obsolete - drives no longer made |
| CD-R, CD-RW | Mb | -RW allows rewrites |
| DVD-R, DVR-RW | Gb | -RW allows rewrites |
| DVD+R, DVD+RW | Gb | Different format to -R, -RW |
Note that -RW media are not as long-lived as -R media, and it's become pretty obvious that -RW media may only last several years, not several decades. In short they're no better than magnetic tapes for longevity unless you specifically buy archival media.
I've basically drifted away from tapes and toward DVD+R and DVD-R as the media of choice for regular backups of datasets. I may add a DDS-4 drive in , because I probably need something to transfer all the old DDS-1 tapes to for long-term storage and DDS-4 is still a nominal standard. However since the development of DDS as a storage medium has halted, there are questions about it's longevity. The c format is no longer developed, so along with the DDS-1 drive these are basically legacy support issues.
I usually use the program tar for Unix archiving on tapes. The program bru has similar (and sometimes more sophisticated) options, but is sometimes less widely available (e.g. no bru on OS X). The basic format is:
tar -cvf tape_drive file1 [file2 ] where this is interpreted as create (c) a tar archive on the tape drive (f tape_drive) using the files directories listed on the remained of the command line. The -v flag makes is verbose - i.e. it lists the files as it archives them. On the SGIs the name of the default tape drive can be omitted. The c tape drive is called /dev/rmt/tps1dc: tar -cvf /dev/rmt/tps1dc file1 [file2 ] Do not attempt to put multiple archives on one tape unless you know exactly what you are doing.Unix tape devices rewind the tape between each command, so multiple tar commands just result in only the most recent archive being put on tape.DVD-R and CD-R archives
In most cases, under Linux, the optical drives are only writable by root, i.e. you will have to get Phil to do such archives. With CD-R (or DVD-R drives with CD-R media) you use mkisofsand cdrecord: /usr/bin/mkisofs -J -R /some/FILESIn spite of \having been through a data compression process, the compressed backup actually has a few advantages over regular backups.
Benefits of backup compression
Because the compressed backup file is smaller than a regular uncompressed backup of the same data, compressing a backup usually implies less I/O for the device it&#;s being backed up by, which translates into a significantly increased backup speed.
Restrictions of backup compression
Along with the benefits of having such an operation possible when doing your backup, there are also restrictions in order for this to happen.
- A media set cannot contain backups that are both compressed and uncompressed.
- Versions of SQL Server which are older than cannot read compressed backups.
- NTbackups cannot share a tape with compressed SQL Server backups.
Performance implications of backup compression
Implicitly, the operation of backup compression requires additional CPU, which translates into a significantly increased CPU usage. This also might have a negative effect on other operations that happen concurrently with the compression operation.
In this situation, and in case you do not want to trade off much of your CPU time for compression, you have the possibility to create a low-priority compressed backup in a session where CPU usage is monitored and managed by the Resource Governor.
In order to get a grasp of what your backup I/O performance is, you can either form devices by evaluating different sorts of performance counters or you can try to isolate the backup I/O.
The evaluation counters you can use to measure the I/O performance of your backups are:
- Windows I/O performance counters, such as the physical-disk counters
- The Device Throughput Bytes/sec counter of the SQLServer:Backup Device object
- The Backup/Restore Throughput/sec counter of the SQLServer:Databses object
Calculate the Compression Ratio of a Compressed Backup
A metric that can help you see the efficiency of your backup is by seeing its compression ratio. In order to be able to calculate the compression ratio of a backup, you will have to use the available values for the backup in the backup_size and compressed_backup_size columns of the backupset history table, as follows:
SELECT backup_size / compressed_backup_size FROM bilin.com.mxsetThe result of this T-SQL query is the compression ratio of your backup. A quick example would be that if a compression ratio is around , that would indicate that you are saving about 75% of disk space.
The compression ratio of a compressed backup is in direct relation with the data that has to be compressed. A variety of factors can impact the compression ratio which you get with your backup. The primary factors that influence this are:
- The type of data you use for the columns/tables that are in your database. For example, character data compress more efficiently than other types of data.
- The consistency of your data among rows on a page. Usually, in the case, a page contains multiple rows in which a field has the same value, compression at a significant level might occur for that specific value. By comparison, this type of database in contrast with a database that contains random data or another database that contains only one large row per page, a compressed backup would approximately have the same size as an uncompressed backup.
- Encrypted data or not. Data that is encrypted has a lower compression rate than its equivalent unencrypted data. If transparent data encryption is used for encrypting an entire database, compressing backups might not reduce their size by much, or even at all.
- In case the database is compressed. If the database has been through a compression process, the operation of compressing the backup has a high chance of not reducing the size by much or even reducing the size at all.
Allocation of space for the Backup file
In the case of backups that will be created through the compression process, the actual size of the final backup file is very much dependant on how compressible the data in the database is, and this fact is unknown before the actual backup operation is finalized.
Therefore, a default step that occurs when backing up a database using compression, is that the Database Engine calculates an approximate size using a pre-allocation algorithm for the backup file. The algorithm pre-allocates a predefined percentage of the current size of the database for the backup file.
In the case in which more space is necessary during the process of backing up, the Database Engine increases the size of the file. If the final size of the compressed backup file is less than the allocated space, at the end of the backup operation, the Database Engine shrinks the file to the actual final size of the backup, thus freeing the additional space it does not require.
In order to allow the backup file to grow only as needed to reach its final size, you have the possibility of using a trace flag, called This trace flag instructs the backup operation to ignore the default backup compression pre-allocation algorithm. This flag is useful only if you need to save on space by allocating only the actual size required for the compressed backup.
However, by using this trace flag for the backup compression operation, there is the possibility of causing a minor performance penalty translated into a possible increase in the duration of the backup operation.
Helpful tutorials
How To : Configure Backup Compression
Macs are easier - with supported drives you just drag files onto the CD icon, then select burn. With unsupported drives you must use some sort of 3rd party software like Toast. Toast is pretty much a drag-and-drop program as well, so it's all fairly intuitive.
Unix Command Line Methods for Moving Files
Here, when I talk about "source" and "destination" I mean the destination machine and directory is that which you want to backup the data TO. The source machine and directory is where you want to copy the data FROM.Increasingly, we eschew tapes and optical media for backups and write them straight to USB or FireWire hard drives. Methods at different synchrotrons differ as to the method of attaching these drives, but it's fairly obvious that attaching it to the machine that holds the data is an advantage since anything that does a lot of network I/O is going to be slower.
If the source disk is readable by the machine holding the destination disk: then you can use simple Unix commands. "cp -R" is the obvious one (recursive copy). Read the man page to cp but it's pretty darn obvious how to use it (cp -R /source/directory/* /destination/directory/.)
If the source disk is on a remote machine then you have a couple of options. If the machine is on a very remote site then you mostly have to use ftp:
cd /the/destination/directory ftp bilin.com.mx (supply username and password) cd /the/source/directory bin prompt mget *.img cd /another/source/directory lcd /another/desination/directory mget *img quit FTP is simple - the mget command grabs files from the current directory on the machine you've FTP'd to, and stuffs them onto the current directory of the machine you've FTP'd from. Bin just ensures that files transfer using binary mode (important), and prompt will make FTP do all it's work in the background. You can move around the remote (source) and local (destination) directory structure using cd and lcd respectively. The secure version of FTP is SFTPwhich has basically the same syntax but a slightly different method of logging in: sftp username@machine Some machines no longer support ftp but will allow sftp connections.The program scp is an alternative to sftp. Basically scp works like a secure version of rcp and allows you to do copies between remote machines. Syntax is as follows:
scp -r 'username@bilin.com.mxe:/the/source/directory/*' /the/destination/directory/. Some elaboration is required. The -r is the "recursive" flag just like -R in "cp -R", so it will copy the specified files including subdirectories. The username@machine syntax is fairly obvious, and the source files are specified as a single path after the colon. It's not possible to specify multiple directories at once using this syntax. The source location is enclosed in single quotes in the above example because otherwise the local shell will interpret the *. You don't want that. You want scp to interpret the * so it knows what files/directories to get. You can use *img if you just want the image files in that directory. Scp is reasonably efficient, shows you what it is doing, and is flexible enough to make me use it as the default method for my file transfers at synchrotrons (e.g. if I'm transferring processing files from the processing machine to my laptop). Scp is rather less efficient if you have lots of files. Also "scp -r" is potentially dangerous since scp follows the linkrather than simply copying the link (like tar, ftp). This means that if you use "ln -s" to make links to other directories, scp will copy the link destination contents as well. This can potentially massively expand the amount copied !!Rsync is also a means to copy files, in that it synchronizes a copy of the source directory onto the destination directory. The upside of it is that if the source directory contents change, the next rsync command updates it. The downside of it is that if you are running rsync automatically, you end up deleting files in the destination directory that you deleted by accident in the source directory
Nevertheless, with that caveat, rsync is often quite efficient for large directory collections:
rsync -azv /the/source/directory/ /the/destination/directory/. will do the trick. Anything new that appears in source will get copied to destination, with the downside that if you uncompress files already in source, the compressed anduncompressed versions are likely to turn up in destination. To make a precise copy of the two directories, include the --delete flag: rsync -azv --delete /the/source/directory/ /the/destination/directory/. with the aforementioned issue that things deleted from source also get deleted from destination.Rsync is easiest to use when the disks are mounted via NFS (or on the same machine). To use rsync between networked machines that don't share NFS mounts, use the ssh protocol flag:
rsync -e ssh -azv --delete /the/source/directory/ user@hostname:/the/destination/directory/. where the -e ssh flag tells rsync to use ssh to connect to remote machines. In principle, if you're not transferring too much data, something like xray3 or xtreme3 accept ssh logins from select hosts.Phil Jeffrey, January - revised July
Compression in BackupAssist&#;
The Microsoft Backup Format does not natively support compression.
However, BackupAssist&#; allows you to compress your backup files using a free program known as 7-Zip.
Figure 1: Compressing backup files with BackupAssist&#;
- Advantages of using compression:
- Fit more data onto your backup device (eg. hard drive, REV drive, etc)
- Disadvantages of using compression:
- Your backup file must be uncompressed before you can perform a restoration
- Your backup will take longer to run, because compression can be slow and is performed as an additional step once the backup has finished
- You require temporary space on your hard drive to perform the compression
- Recommended for: situations where the size of your backup is important - for example, if you copy your backup file to a remote server via VPN or FTP, then compressing the file will reduce the transfer time.
How the compression works
BackupAssist&#; will perform the backup of your data to a backup file (this file will usually end in the extension .bkf). Then BackupAssist&#; will compress the backup file using one of the compression methods explained below - this will usually result in a 25% to 50% space saving.
When you want to restore your data, you should uncompress your backup file (also explained below) and then run the Windows Backup program to restore you data from the uncompressed backup file.
BackupAssist&#; uses the program 7-Zip to perform backups. This allows you to compress your files using a variety of compression methods, as described below:
- ZIP - the most common compression method, that's also built into Windows XP and Server. The ZIP standard has a severe limitation - backup files must be under 4 gig in size. ZIP compression will not work if the file is greater than 4 gig in size. (A new standard, ZIP, allows for huge files to be compressed and is supported by WinZIP, but is not supported by 7zip or Windows XP / )
- 7z - an open compression format that provides the best compression, and can compress large backup files
- GZIP - an open compression format that can compress large backup files
- BZIP2 - an open compression format that can compress large backup files
| Compression method | Small backup file | Large backup file | ||
|---|---|---|---|---|
| No compression | Original size: 30, KB | Original size: 6,, KB | ||
| zip compression | 19, KB | compression % saving | 4,, KB | compression % saving |
| 7z compression | 16, KB | compression % saving | 3,, KB | compression % saving |
| gzip compression | 19, KB | compression % saving | 4,, KB | compression % saving |
| bzip2 compression | 19, KB | compression % saving | 4,, KB | compression % saving |
The data in the backup files are:
- Small backup file - Backup of our websites - HTML and graphics
- Large backup file - Backup of our entire file server - system, registry, C:\ drive and data
Compression Encryption
BackupAssist&#; also allows you to encrypt your backup file with a password that must be later entered to extract the backup file to complete a restoration of your data.Please note: that if you choose to enable encryption for your backup file that you use a password that can easily be remembered.
How to uncompress your backup file
If you are using ZIP compression, then commercial ZIP programs such as WinZIP, PKZip will perform the decompression.
For the other formats, you have several options
- Use the bilin.com.mx command line utility that is distributed with BackupAssist&#;. (Recommended for system administrators and advanced users)
- Download a free utility called TugZIP - a very user-friendly and intuitive compression utility.
- Download the Windows version of 7-Zip and use the user-interface which is also quite user friendly.
The important thing is that all the compression methods supported in BackupAssist&#; are open standards, and there are a variety of free programs that can be used to uncompress your backup file. This means that your data is not locked away in a proprietary format like it would normally be in other backup software packages.
You can watch a thematic video
Backup Exec 21 How to use compression in a backup jobVery: Compression and Backup
| Crack for drivermax Crack Key For U |
| Compression and Backup |
| Compression and Backup |
| Compression and Backup |
Should We Compress SQL Server Backups?
Last week we covered five reasons why log shipping should be used. I got a great question that I thought should be answered here in a short blog post. The question is &#;how do you configure transactional log shipping to include compression when taking the transactional log backups?&#;
First, a better question is &#;should we be compressing our SQL Server Backups?&#; In a second we will address log shipping, but first I wanted to just focus on compressing backups. The Compression and Backup is &#;it depends&#; (typical DBA response). There is CPU overhead for utilizing compression. We will not focus too much on this here as you can enable resource governor to limit CPU usage for your backups.
Today, Compression and Backup, we will focus on capacity Compression and Backup misleading storage saving results due to enabling backup compression. Looking at a traditional DBA role, you might have exposure to view your server, drives, and the size of the backups. Therefore, taking a compressed backup leads you to likely see less storage being used for the backup file compared to other backups of the same database. This is typically the goal for backup compression to reduce storage space consumed by backups.
Another question you should be asking yourself is, &#;What storage system is being used for your SQL Server backups?&#; For example, storage access networks (SAN) might have its own compression and native SQL Server backup compression might hurt the impact of the SAN&#;s compression, which could cause more RAW storage to be used. Therefore, there really isn&#;t a silver bullet to always use SQL Server backup compression in every environment, Compression and Backup. You need to understand if there is any compression built into the storage used for your backups, and understand how backup compression impacts the storage system before deciding to utilize backup compression.
Okay, now that we got our disclaimer out of the way, Compression and Backup. Here is how you would enable backup compression for transactional log shipping.
Enabling backup compression with T-SQL is as simple as just adding the compression option. The following is a common example of backing up a database with compression.
BACKUP DATABASE [LSDemo] TO DISK = N'c:\somewhere\bilin.com.mx' WITH COMPRESSIONIf all of your backups for an instance of SQL Server go to storage where utilizing native SQL Server compression provides improvement, then you can consider enabling compression by default. Therefore, all backups taken on this instance of SQL Server would then use backup compression by default unless another option was given during the T-SQL execution of the backup command.
EXEC bilin.com.mx_configure N'backup compression default', N'1' GO RECONFIGURE WITH OVERRIDE GORelated
Tags: backup, compression, log Compression and Backup
Compression and Backup
In transferring data from synchrotrons, compressing files is essentialto reduce space and speed up transfers. In many cases on the home disks, much space can be saved if you compress some of your larger or infrequently used files. (Deleting temporary files etc will also help).Compressing Files
With compress, compressed files have a .Z extension: compress *img - compress all files matching pattern uncompress *img.Z - uncompresses all files with .Z extension With gzip, compressed files have a .gz extension gzip *img - gzip all files matching pattern gunzip *bilin.com.mx - gunzip all those files With bzip2, compressed files have a .bz2 extension bzip2 *img - bzip2 all files matching pattern bunzip2 *bilin.com.mx2 - bunzip2 all those filesFinding large or old files
If you're running out of space on your home disk, a sensible approach is to compress files that you don't use often. The biggest gain is made when applying this to large files. In order to find those files, use the findcommand: find ~ -size + -print which prints (-print) the names of all files from your home directory (~) on down that are greater (+) than blocks. If you omit the + it only prints files that are blocks, and that's of less use. The command: find ~ -mtime + -print prints the names of all files that were modified at least days ago. You can combine these features: find ~ -size + -mtime + -print which prints only large (> blocks), old (> 1 year) files. To compress these files using gzip, use: find ~ -size + -type f -mtime + -print -exec gzip '{}' \; gzip will whine if some of the files selected are already gzipped, so you can use more elaborate find syntax (-not -name '*.gz') if you like, or just ignore the error messages. I include "-type f" in the above command just to stop gzip even trying to compress links or directories - it won't but it will Compression and Backup potential error messages. Consult the manual page to find for more interesting options and features - really a very powerful program.Which compression program?
The old Unix compression program was compressis reasonably efficient but does no error checking. The newer Free Software Foundation program gzipis more efficient, does error checking and is widely available for all Unixes. An even newer program bzip2is a slower than gzip but does an even tighter job of compressing. It's available on Linux, OS X and I have installed it on our SGIs. I most frequently use gzip, but for situations where disk space is at a premium, bzip2 is probably better unless you are short on CPU.Here's a comparison of compression efficiencies and times on NINE data frames from X9A. This is in Linux on a local SCSI disk, timings averaged over three operations, default program options:
| Program | Time Taken | Final Size | Fraction of original size |
|---|---|---|---|
| compress | Compression and Backup | ||
| gzip | sec | ||
| bzip2 | sec |
Actual compressed sizes depend on the strength of the data. However note that bzip2 is much more efficient at Compression and Backup on these files at the cost of a whole lot of CPU. For decompression of these same frames (less of an issue):
| Program | Time Taken |
|---|---|
| uncompress | sec |
| gunzip | sec |
| bunzip2 | sec |
Note that for ASCII files (e.g. PDB files) often much greater compression efficiencies can be achieved. Gzip or bzip2 are always preferable to compress because of their error checking of Compression and Backup archive.
Testing archive integrity
If you are feeling sufficiently paranoid, or you suspect that data transfer may not be correct, you can test integrity of compressed frames by some variant on the following, Compression and Backup, which takes all .gz files in the current directory and reads them, Compression and Backup, disposing of the output. Error messages (e.g, Compression and Backup. corrupted files) are echo'd to the terminal. find. -name '*gz' -print -exec zcat '{}' \; > /dev/null zcat should be replaced by gzcat on the SGI.Note that very recent experience with older machines is that they can sometimes silently fail on writing files that they should otherwise have no problem with. It's not clear how this happens, but it certainly happened at APS beamlime 8BM. It may also have happened with xtreme4 locally.
Backup Options
We have a variety of drives within the floor: DDS-1 tape drive (SGI - currently Xtreme4), DDS-4 tape drive in Nikolov lab, Exabyte c tape drive (Ximpact1 - now unplugged), CD-RW (most Macs) and DVD-R (Facility G4, some Linux workstations, some Macs). The advantages of tape are their generally larger capacities. The advantages of optical media is that they are random access - you can read the last file off the CD-R quickly, whereas you have the read the entire tapeto get to the last file. Tapes are inherently re-usable. CD-R and DVD-R are not, and even their -RW versions have limited overwrite counts.| Media | Capacity | Notes |
|---|---|---|
| DDS-1 4mm DAT tape | Gb | Obsolete - drives no longer made |
| DDS-4 4mm DAT tape | Gb | Drives cannot read DDS-1 ? |
| Exabyte c 8mm tape | Gb | Obsolete - drives no longer made |
| CD-R, CD-RW | Mb | -RW allows rewrites |
| DVD-R, Compression and Backup, DVR-RW | Gb | -RW allows rewrites |
| DVD+R, DVD+RW | Gb | Different format to -R, -RW |
Note that -RW media are not as long-lived as -R media, Foobar2000 1.6.2 Free Download for (Win+Mac) it's become pretty obvious that -RW media may only last several years, not several decades. In short they're no better than magnetic tapes for longevity unless you specifically buy archival media.
I've basically drifted away from tapes and toward DVD+R and DVD-R as the media of choice for regular backups of datasets. I may add a DDS-4 drive inbecause I probably need something to transfer all the old DDS-1 tapes to for long-term storage and DDS-4 is still a nominal standard, Compression and Backup. However since the development of DDS as a storage medium has halted, there are questions about it's longevity. The c format is no longer developed, so along with the DDS-1 drive these are basically legacy support issues.
I usually use the program tar for Unix archiving on tapes. The program bru has similar (and sometimes more sophisticated) options, but is sometimes less widely available (e.g. no bru on OS X). The basic format is:
tar -cvf tape_drive file1 [file2 ] where this is interpreted as create (c) a tar archive on the tape drive (f tape_drive) using the files directories listed on the remained of the command line. The -v flag makes is verbose - i.e. it lists the files as it archives them. On the SGIs the name of the default tape drive can be omitted. The Compression and Backup tape drive is called /dev/rmt/tps1dc: tar -cvf /dev/rmt/tps1dc file1 [file2 ] Do not attempt to put multiple archives on one tape unless you know exactly what you are doing.Unix tape devices rewind the tape between each command, so multiple tar commands just result in Compression and Backup the most recent archive being put on tape.DVD-R and CD-R archives
In most cases, under Linux, the optical drives are only writable by root, i.e. you will have to get Phil to do such archives. With CD-R (or DVD-R drives with CD-R media) you use mkisofsand cdrecord: /usr/bin/mkisofs -J -R /some/FILES /usr/bin/cdrecord -v -speed=4 -dev=2,0,0 - With DVD-R drives with DVD-R or DVD+R media on Linux you use: ~xtal/dvd+rw-tools/growisofs -Z /dev/scd1 -J -R /some/FILES There's a more thorough description of all this in my Linux Setupnotes.Macs are easier - with supported drives you just drag files onto the CD icon, then select burn. With unsupported drives you must use some sort of 3rd party software like Toast. Toast is pretty much a drag-and-drop program as well, Compression and Backup, so it's all fairly intuitive.
Unix Command Line Methods for Moving Files
Here, when I talk about "source" and "destination" I mean the destination machine and Compression and Backup is that which you want to backup the data TO. The source machine and directory is where you want to copy the data FROM.Increasingly, we eschew tapes and optical media for backups and write them straight to USB or FireWire hard drives. Methods at different synchrotrons differ as to the method of attaching these drives, but it's fairly obvious that attaching it to the machine that holds the data is an advantage since anything that does a lot of network I/O is going to be slower.
If the source disk is readable by the machine holding the destination disk: then you can use simple Unix commands. "cp -R" is the obvious one (recursive copy). Read the man page to cp but it's pretty darn obvious how to use it (cp -R /source/directory/* /destination/directory/.)
If the source disk is on a remote machine then you have a couple of options. If the machine is on a very remote site then you mostly have to use Compression and Backup
cd /the/destination/directory ftp bilin.com.mx (supply username Compression and Backup password) cd /the/source/directory bin prompt mget *.img cd /another/source/directory lcd /another/desination/directory mget *img quit FTP is simple - the mget command grabs files from the current directory on the machine you've FTP'd to, and stuffs them onto the current directory of the machine you've FTP'd from. Bin just ensures that files transfer using binary mode (important), Compression and Backup, and prompt will make FTP do all it's work in the background. You can move around the remote (source) and local (destination) directory structure using cd and lcd respectively. The secure version of FTP is SFTPwhich has basically the same syntax but a slightly different method of logging in: sftp username@machine Some machines no longer support ftp but will allow sftp connections.The program scp is an alternative to sftp. Basically scp works Compression and Backup a secure version of rcp and allows you to do copies between remote machines. Syntax Compression and Backup as follows:
scp -r 'username@bilin.com.mxe:/the/source/directory/*' /the/destination/directory/. Some elaboration is required. The -r is the "recursive" flag just like -R in "cp -R", so it will copy the specified files including subdirectories. The username@machine syntax is fairly obvious, and the source files are specified as a single path after the colon. It's not possible to specify multiple directories at once File Scavenger V6.1 Crack +Registration Key 2021 Free Activators this syntax. The source location is enclosed in single quotes in the above example because otherwise the local shell will interpret the *. You don't want that. You want scp to interpret the * so it knows what files/directories to get, Compression and Backup. You can use *img if you just want the image files in that directory. Scp is reasonably efficient, Compression and Backup, shows you what it is doing, and is flexible enough to make me use it as the default method for my file transfers at synchrotrons (e.g. if I'm transferring processing files from the processing machine to my laptop), Compression and Backup. Scp is rather less efficient if you have lots of files. Also "scp -r" is potentially dangerous since scp follows the linkrather than simply copying the link (like tar, ftp). This means that if you use "ln -s" to make links to other directories, scp will copy the link destination contents as well. This can potentially massively expand the amount copied !! Compression and Backup is also a means to copy files, Compression and Backup, in that it synchronizes a copy of the source directory onto the destination directory. The upside of it is that if the source directory contents change, the next rsync command updates it. The downside of it is that if you are running rsync automatically, Compression and Backup, you end up deleting files in the destination directory that you deleted by accident in the source directoryNevertheless, with that caveat, rsync is often quite efficient for large directory collections:
rsync -azv /the/source/directory/ /the/destination/directory/. will do the trick. Anything new that appears in source will get copied to destination, with the downside that if you uncompress files already in source, the compressed anduncompressed versions are likely to turn up in destination. To make a precise copy of the two directories, include the --delete flag: rsync -azv --delete /the/source/directory/ /the/destination/directory/. with the aforementioned issue that things deleted from source also get deleted from destination.Rsync is easiest to use when the disks are mounted via NFS (or on the same machine). To use rsync between networked machines that don't share NFS mounts, use the ssh protocol flag:
rsync -e ssh -azv --delete /the/source/directory/ user@hostname:/the/destination/directory/, Compression and Backup. where the -e ssh flag tells rsync to use ssh to connect to remote machines. In principle, if you're not transferring too much data, something like xray3 or xtreme3 accept ssh logins from select hosts.Phil Jeffrey, January - revised July
: LZ4 r Out of the three compression algorithms that are supported, this is the most efficient one, typically taking the shortest backup and restore times with the lowest CPU cost. See lz4—Extremely Fast Compression algorithm for more details, including a comparison with other compression algorithms.
: LZMA Out of the three supported compression algorithms, this typically provides the highest compression ratio; but it is also far more expensive in terms of CPU cost than the other two options. Thus we do not recommend Compression and Backup for active systems, but only for off-hour or inactive databases, or where I/O rates are extremely low.
: (For MySQL Enterprise Backup and later) Enables support for transparent page compression for InnoDB tables for directory backups, which means that when the target platform for the mysqlbackup backup or restore operation supports hole punching, mysqlbackup keeps the punched holes in the page-compressed InnoDB files it transfers.
Limitations: The feature is NOT supported in the following cases, for which punched holes are removed from the InnoDB files:
For single-file backups.
For TTS, incremental, compressed, or encrypted backups.
When a backup is not created in a file system (for example, when cloud storage is used to save the backup), or when the file system does not support sparse files.
For those pages of InnoDB data files that are modified by the redo log in an operation.
When the feature is enabled but hole punching fails, mysqlbackup issues a warning message after the operation is completed; for example:
Or:
A backup can be taken with and then be restored later without using the feature; the reverse is also true: a backup taken without using can be restored later with the feature, Compression and Backup.
File compression is a method of reducing the size of a file without a significant loss of information in order to save storage space and easy transfer of the files. Database compression is a method of reorganizing data to save space and increase performance. It could be a file or database, compression generally is meant to compress the size and speed up the file transfer.
There are two main types of compression namely; Lossy and lossless compression. This blog will provide insight into Compression and Backup and database compression with a short summary of the compression algorithms.
Lossy Compression
Lossy compression removes insignificant information and commonly done on video and audio files to reduce the file size. The loss is usually not noticeable, however, if the file is heavily compressed, then there would be a noticeable drop in quality.
This compression is a great option for image or video uploads, because it preserves the required information and reduces the file size but makes it easier for transfer and the loss in quality is usually not very noticeable to the user. This means Lossy compression reduces the quality of the media, but it is not visible to naked eye. The picture below is a simple example of how a PNG file is compressed to a JPEG file. While the size is reduced, Compression and Backup is not much of a visible effect from the output.
Lossy compression is not ideal for files where the details of the information are crucial (like in spreadsheets and word documents) because the compression can mess Compression and Backup the output; meaning when the file is decompressed the text might be garbled leading to loss of information.
Lossless Compression
Lossless compression reduces the file size without losing any information. The algorithm works on the principle of eliminating or handling redundancy. It can be applied to both text and image files. As there is no loss of information, when the file is decompressed, Compression and Backup, it will restore it to its original state.
This is a perfect technique for text compression where there is no compromise for loss of any data after decompression. Zip file program in Windows uses this method of compression.
Database Compression
Compression for databases can be done using lossy or lossless technique as well. The type of compression to be applied is decided based on the data stored in the database but most database applications use lossless compression to preserve the quality of data. Database applications employ different types of compression algorithms like run-length encoding, prefix encoding, compression using clustering, sparse matrices, dictionary encoding or any own proprietary compression methods.
Popular Compression Algorithms
Run-Length Encoding (RLE)
Run-Length Encoding is a lossless compression technique which scans data sequentially for repetitive value and Compression and Backup occurrence then encodes to a sequence of value and its count.
Example: WWWWHHHHYYYY
With RLE algorithm applied to the above line, Compression and Backup, it will be encoded to the following: 4W4H4Y
Prefix Encoding
This algorithm also removes redundant data but its rather difficult to implement, Compression and Backup. This compression technique uses prefix encoding to compress and then transfer the data.
Example
In the example Compression and Backup the data has the same prefix thus it was simple to choose the prefix, however usually data The problem with this compression is selecting the right prefix for data without much of similarity. This compression algorithm is good for date and time, and geolocation as these data have a good prefix pattern.
Dictionary Compression
Dictionary compression algorithms replace long strings with shorter codewords. The codewords are compiled into a dictionary and stored in the header row. As an example, let’s say a dictionary has codeword value as 1-life, 2-great, 3-and, 4-but. Now if the file content is “Life is great and fun but complicated”. These words will be replaced with indexes from the dictionary. Now the file will have 1is23fun4complicated. Use the dictionary to decompress the file to its original form, Compression and Backup. If the file has many Compression and Backup matching the values in the dictionary, Compression and Backup, then there will be a significant reduction in the file size.
Benefits of Database Compression
- Compression is used to reduce the overall database size to save database storage space. The compression rate is better if there is a lot of repetition in data values or there are many tables with less data or zero value data.
- Read speed is faster when the file size is small, however, the write operation might be a little slower because the data needs to be decompressed before the write operation.
- Resource utilization is lesser because more data can fit in memory or buffer.
Disadvantages of Database Compression
- Compression algorithms always build a keyword dictionary which is a part of the compressed database. If the database is small, there is a possibility that with the Compression and Backup dictionary the file size is larger than the original database.
- Extra overhead cost with compression and decompression because of extra CPU/ memory utilization.
- It is not recommended to compress numerical data and non-repetitive strings as this might increase or decrease the file size.
File Compression vs Database Compression
File data compression looks at how to minimize the value of the data items to reduce the size. Database compression, on the other hand, is an aggregate compression because it compresses data, indices, views, clusters and heaps. The compression is done on data across rows, columns, and at field level. BLOB data such as Image, video, and audio stored in the database can be compressed using the lossy compression.
Conclusion
In summary, compression is a technique to reduce the size of the file or database, Compression and Backup. This is Compression and Backup useful to reduce resource utilisation as well as save storage costs, Compression and Backup. A smaller size file or database is easy to transfer and speed operation processing. Not only this, Compression and Backup, a smaller file requires less memory and CPU utilization which is also another means to save overhead cost and increase data processing power. Large scale applications like Facebook, Google, or Oracle uses high-end compression algorithms like ZStandard, Compression and Backup, Snappy, XPress, and Oracle Advanced Compression to perform compression for the large data sets.
In spite of \having been through a data compression process, the compressed backup actually has a few advantages over regular backups.
Benefits of backup compression
Because the compressed backup file is smaller than a regular uncompressed backup of the same data, compressing a backup usually implies less I/O for the device it&#;s being backed up by, which translates into a significantly increased backup speed.
Restrictions of backup compression
Along with the benefits of having such an operation possible when doing your backup, there are also restrictions in order for this to happen.
- A media set cannot contain backups that are both compressed and uncompressed.
- Versions of SQL Server which are older than cannot read compressed backups.
- NTbackups cannot share a tape with compressed SQL Server backups.
Performance implications of backup compression
Implicitly, the operation of backup compression requires additional CPU, which translates into a significantly increased CPU usage. This also might have a negative effect on other Designs Crack Key For U that happen concurrently with the Compression and Backup operation.
In this situation, Compression and Backup, and in case you do not want to trade off much of your CPU time for compression, Compression and Backup, you have the possibility to create a low-priority compressed backup in a session where CPU usage is monitored and managed by the Resource Governor.
In order to get a grasp of what your backup I/O performance is, you can either form devices by evaluating different sorts of performance counters or you can try to isolate the backup I/O.
The evaluation counters you can use to measure the I/O performance of your backups are:
- Windows I/O performance counters, such as the physical-disk counters
- The Device Throughput Bytes/sec counter of the SQLServer:Backup Device object
- The Backup/Restore Throughput/sec counter of the SQLServer:Databses object
Calculate the Compression Ratio of a Compressed Backup
A metric that can help you see the efficiency of your backup is by seeing its compression ratio. In order to be able to calculate the compression ratio of a backup, you will have to use the available values for the backup in the backup_size and compressed_backup_size columns of the backupset history table, as follows:
SELECT backup_size / compressed_backup_size FROM bilin.com.mxsetThe result of this T-SQL query is the compression ratio of your backup. A quick example would be that if a compression ratio is around , that would indicate that you are saving about 75% of disk space.
The compression ratio of a compressed backup is in direct relation with the data that has to be compressed. A variety of factors can impact the compression ratio which you get with your backup. The primary factors that influence this are:
- The type of data you use for the columns/tables that are in your database, Compression and Backup. For example, character data compress more efficiently than other types of data.
- The consistency of your data among rows on a page. Usually, in the case, a page contains multiple rows in which a field has the same value, compression at a significant level might occur for that specific value. By comparison, this type of database in contrast with a database that contains random data or another database that contains only one large row per page, a compressed backup would approximately have the same size as an uncompressed backup.
- Encrypted data or not. Data that is encrypted has a lower compression rate than its equivalent unencrypted data. If transparent data encryption is used for encrypting an entire database, compressing backups might not reduce their size by much, or even at all.
- In case the database is compressed. If the database has been through a compression process, the operation of compressing the backup has a high chance of not reducing the size by much or even reducing the size at all.
Allocation of space for the Backup file
In the case of backups that will be created through the compression process, the actual size of the final backup file is very much dependant on how compressible the data in the database is, and this fact is unknown before the actual backup operation is finalized.
Therefore, a default step that occurs when backing up a database using compression, is that the Database Engine calculates an approximate size using a pre-allocation algorithm for the backup file. The algorithm pre-allocates a predefined percentage of the current size of the database for the backup file.
In the case in which more space is necessary during the process of backing up, the Database Engine increases the size of the file. If the final size of the compressed backup file is less than the allocated space, at the end of the backup operation, the Database Engine shrinks the file to the actual final size of the backup, thus freeing the additional space it does not require.
In order to allow the backup file to grow only as needed to reach its final size, you have the possibility of using a trace flag, called This trace flag instructs the backup operation to ignore the default backup compression pre-allocation algorithm. This flag is useful only if you need to save on space by allocating only the actual size required for the compressed backup.
However, by using this trace flag for the backup compression operation, there is the possibility of causing a minor performance penalty translated into a possible increase in the duration of the backup operation.
Helpful tutorials
How To : Configure Backup Compression
Compressed backups
Backups take a lot of space, which can cost quite a lot of money. To reduce the space needed, the backups can be compressed. There are several ways of doing this. Some programs have support for for compression built in; for example, the () option for GNU tar pipes the whole backup through the gzip compression program, before writing it to the backup medium.
Unfortunately, compressed backups can cause trouble. Due to the nature of Compression and Backup compression works, if a single bit is wrong, all the Compression and Backup of the compressed data will be unusable. Some backup programs have some Compression and Backup in error correction, but no method can handle a large number of errors. This means that if the backup is compressed the way GNU tar does it, with the whole output compressed as a unit, a single error makes all the rest of the backup lost. Backups must be reliable, and this method of compression is not a good idea.
An alternative way is to compress each file separately. This still means that the one file is lost, but all other files are unharmed. The lost file would have been corrupted anyway, so this situation is not much worse than not using compression at all, Compression and Backup. The afio program (a variant of cpio) can do this.
Compression takes some time, which may make the backup program unable to write data fast enough for a tape drive. Compression and Backup can be avoided by buffering the output (either internally, if the backup program if smart enough, or by using another program), Compression and Backup, but even that might not work well enough. This should only be a problem on slow computers.
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