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Data Compression and Deduplication

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To decrease traffic and disk space required for storing backup files, Veeam Backup & Replication provides mechanisms of VM data compression and deduplication.

Data Compression

Data compression decreases the size of created backups but affects duration of the backup procedure. With the new data compression algorithm used in 7.0, Veeam Backup & Replication allows you to select one of the following compression levels:

None compression level is recommended if you use storage devices with hardware compression and deduplication tools to store created backups.
Dedupe-friendly is an optimized compression level for very low CPU usage. It is recommended if you want to decrease the proxy load.
Optimal (default setting) is the recommended compression level providing the best ratio between the size of the backup file and time of the backup procedure.
High compression level provides additional 10% compression ratio over Optimal, but at the cost of about 10x higher CPU usage.
Extreme compression provides the smallest size of the backup file but reduces backup performance. We recommend that you run backup proxies on computers with modern multi-core CPUs (6 cores recommended) if you intend to use the extreme compression.



If you are upgrading to 7.0 from the previous version of Veeam Backup & Replication, consider that compression level you have previously set for your jobs will be preserved (compression level named Optimal in version 6.5 will appear as High in the user interface after the upgrade). However, all the newly created jobs will have the new compression level in effect.


You can apply deduplication when backing up multiple VMs that have similar data blocks (for example, if VMs were created from the same template) or great amount of free space on their logical disks. Veeam Backup & Replication does not store zero byte blocks or space that has been pre-allocated but not used. With deduplication, identical blocks or blocks of free space are eliminated, which decreases the size of the created backup file.

Depending on the type of storage you select as a backup target, Veeam Backup & Replication uses data blocks of different size to process VMs, which optimizes the size of a backup file and job performance. You can choose one of the following storage optimization options:

The Local target (16 TB + backup files) option is recommended for backup jobs that can produce very large full backup files — larger than 16 TB.
If you select to use data blocks of small size to dedupicate a large backup file, the backup file will be cut into a great number of data blocks. As a result, Veeam Backup & Replication will produce a very large deduplication metadata table which can potentially overgrow memory and CPU resources of your backup repository. For backup files over 16 TB, it is recommended to choose the Local target (16 TB + backup size) option. With this option selected, Veeam Backup & Replication will use data blocks of 8 MB. Large data blocks produce a smaller metadata table that requires less memory and CPU resources to process. Note, however, that this storage optimization option will provide the lowest deduplication ratio and the largest size of incremental backup files.
The Local target option is recommended for backup to SAN, DAS or local storage. The SAN identifies larger blocks of data (1024 KB) and therefore can process large amounts of data at a time. This option provides the fastest backup job performance but reduces the deduplication ratio,  because with larger data blocks it is less likely to find identical blocks.
The LAN target option is recommended for backup to NAS and onsite backup. It provides a better deduplication ratio and reduces the size of a backup file because of reduced data block sizes (512 KB).
The WAN target option is recommended if you are planning to use WAN for offsite backup. Veeam Backup & Replication will use small data blocks (256 KB), which will result in the maximum deduplication ratio and the smallest size of backup files, allowing you to reduce the amount of traffic over the WAN connection.

Changing Data Compression and Deduplication Settings

You can change compression and deduplication settings for existing backup jobs. New settings will not have any effect on previously created backup files in the backup chain. They will be applied to new backup files created after the settings were changed.

To apply new deduplication settings, you must create an active full backup after you change deduplication settings. Veeam Backup & Replication will use the new block size for the active full backup and subsequent backup files in the backup chain.
Compression settings are changed on the fly. You do not need to create a new full backup to use new settings — Veeam Backup & Replication will automatically apply the new compression level to newly created backup files.

However, if you use the reversed incremental backup method, the newly created backup files will contain a mixture of data blocks compressed at different levels. For example, you have a backup job that uses the reversed incremental backup method and the Optimal level of data compression. After several job sessions, you change the data compression level to High. In the reversed incremental backup chains, the full backup file is rebuilt with every job session to include new data blocks. As a result, the full backup file will contain a mixture of data blocks: data blocks compressed at the Optimal level and data blocks compressed at the High level.

If you want the newly created backup file to contain data blocks compressed at one level, you can perform active full backup. Veeam Backup & Replication will retrieve data for the whole VM image from the production infrastructure and compress it at the new compression level. All subsequent backup files in the backup chain will also use the new compression level.

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