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I want to reclaim disk space using the DDB space reclamation feature, but how can I see how much space can be reclaimed?

  • 30 December 2020
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I am running low space.  I want to run disk reclamation. If I run this, how much space can I be saving?

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Best answer by Emils 31 December 2020, 01:06

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Hi @samtula 

Sure you can, this will depend on the reclamation level selected during the space reclamation job.

Let me explain how.

Quick DDB Verification can be used to determine how much space can be recovered with DDB Space Reclamation. Once a Quick DDB Verification is run, the amount of reclaimable space can be found in the DDBMntPathInfo.log log file on the Media Agent. 

The log will report the reclaimable space for each reclamation level. 

DDBMntPathInfo.log – output should appear similar to this: 
Reclaimable: @ 20% [828664613724 (771.75 GB),  0.76%], @ 40% [747364145768 (   696.04 GB),  0.68%]

@ 60% [   627033026654 (   583.97 GB),  0.57%], @ 80% [   288800748668 (   268.97 GB),  0.26%]

 

The above logline explains how much space will be reclaimed depending on the reclamation level selected during the space reclamation job, by default it's set to slider 3 (40%).

 

Reclamation Level: Use this slider to select the level of reclamation to be done. On the slider the numbers indicate the percentage of unused data blocks that can be defragmented.

  • 1 is equal to 80% (Least aggressive reclamation, low I/O on the disk)
  • 2 is equal to 60%
  • 3 is equal to 40%
  • 4 is equal to 20% (Most aggressive reclamation, higher I/O on the disk)

For example: By default the slider is set at 3. This indicates that the data files that have 40% or more of invalid data blocks (unused space) and 60% or less of valid data blocks will be selected for defragmentation to reclaim the unused space.

However, if you set the slider to 4, then the data files that have 20% or more of invalid data blocks (unused space) and 80% or less of valid data blocks will be selected for defragmentation. This will result in a very high I/O on the disk for reclaiming only 20% or more of the unused space. 

 

Please check out the following Commvault documentation link for more information under the heading Reclaim idle space on Mount Paths

If that answers your question, feel free to mark this post as the correct answer.

Thank you

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