VTL Data Deduplication Best Practices

The following are the recommendations to get the maximum data deduplication ratios with the VTL data deduplication feature

  • Disable software data compression by the backup application
  • Enable hardware compression for the tape drive to maximize space savings
  • Disable multiplexing of backup streams
  • Disable encryption of backup streams
  • Disable data deduplication by the backup application itself

Tape Block Size

The block size used to write to tape plays an important part in deduplication ratios achieved. The simple rule is that larger the block size the higher the deduplication ratios.
The following lists the default block size used by different backup applications.

NOTE: For certain backup applications a newer block size will only be picked up after a relabeling of the virtual tape

Symantec NetBackup

The default block size used for tape is 64K. This is not optimal for data deduplication and can be increased to 256K by specifying SIZE_DATA_BUFFERS as 256K

IBM Tivoli Storage Manager

The default block size used is 256K and is optimal for data deduplication

Computer Associates ARCServe

The default block size used for tape is 64K and is not optimal for data deduplication. This can be changed to 256K as described in https://support.ca.com/cadocs/0/CA%20ARCserve%20%20Backup%20r16-ENU/Book...

CommVault Simpana

The default block size used for tape is 64K and is not optimal for data deduplication. This can be increased to 256K in the "Data Path Properties" of a library. For example see "Increasing Block Size" section in http://documentation.commvault.com/hds/v10/article?p=features/performanc...

Symantec Backup Exec

The default block size used for tape is 64K and is not optimal for data deduplication. This can be changed for each drive by selecting its properties and changing the "Block Size" to 256K

HP Data Protector

The default block size used is 256K and is optimal for data deduplication

EMC NetWorker

The default block size used is 128k which is good but may be increased to 256K for optimal data deduplication

Dell/Quest Netvault

The default block size used is 32k which is not optimal for data deduplication. This can be changed for each drive by selecting its properties and changing the "Block Size" to 256K