Forum Discussion

Krutina's avatar
Krutina
Level 3
11 years ago

Dedupe Query

Hi   I got a doubt when i were to configure a backup to a MSDP. Intention here is to create a fullbackup every week end and an incremental on the week days. Retention of weekly would be 2 weeks...
7.5
Agents
Backing Up
Backup and Recovery
Basics
Best Practice
Configuring
Evaluating
Managing Backup Devices
NetBackup
  • RonCaplinger's avatar
    RonCaplinger
    11 years ago

    The space occupied by the 1st copy would likely be less than the original size, but that all depends on the data.  Deduplication looks at "blocks" of data, not file-by-file.  Block size will vary.  A single file may be one block, or it could be multiple blocks, depending on how the deduplication engine happens to examine the incoming data.  This can also make estimation difficult.  If your data being backed up would compress well with something like WinZip, then it will likely deduplicate well, although the two technologies are very different from a compression standpoint.  However, if your data would not compress very much, such as video, audio, or .jpg files, then deduplication probably won't save any space. 

    An example where deduplication would be really helpful is if you were to back up the C:\windows directory of 10 servers.  The first backup of the very first server would likely take the same space in the MSDP as the original data on the first server, because there isn't a lot of duplicate strings of characters in those files.  But the backup of the second through the tenth servers' C:\windows directory would probably deduplicate enough to save 99% or more every time.  

RonCaplinger's avatar
RonCaplinger
Level 6
11 years ago

The space occupied by the 1st copy would likely be less than the original size, but that all depends on the data.  Deduplication looks at "blocks" of data, not file-by-file.  Block size will vary.  A single file may be one block, or it could be multiple blocks, depending on how the deduplication engine happens to examine the incoming data.  This can also make estimation difficult.  If your data being backed up would compress well with something like WinZip, then it will likely deduplicate well, although the two technologies are very different from a compression standpoint.  However, if your data would not compress very much, such as video, audio, or .jpg files, then deduplication probably won't save any space. 

An example where deduplication would be really helpful is if you were to back up the C:\windows directory of 10 servers.  The first backup of the very first server would likely take the same space in the MSDP as the original data on the first server, because there isn't a lot of duplicate strings of characters in those files.  But the backup of the second through the tenth servers' C:\windows directory would probably deduplicate enough to save 99% or more every time.