OST Media reclamation in Backup Exec 2010 R3 (and 2010 R2 Hotfix 154003) cause jobs to go in to the queued state for a long time.

Article:TECH159843  |  Created: 2011-05-11  |  Updated: 2014-04-03  |  Article URL http://www.symantec.com/docs/TECH159843
Article Type
Technical Solution


Issue



Reclaiming space in a deduplication folder has been changed in Backup Exec 2010 R2 Hotfix 154003 and Backup Exec 2010 R3 releases.  Media Management has been modified to more aggressively reclaim space taken by expired media that are in a deduplication folder or on a deduplication appliance.


Cause



When a piece of Backup Exec media is erased from a deduplication device, it does not result in immediate availability of space on the device.  It takes time to go through databases and the careful process of ensuring that the data associated with the erased piece of media is only removed if it isn't being referenced by other media that is still in use by Backup Exec.  This is different from a B2D folder where Backup Exec can erase expired media on the fly and immediately have space available for a backup operation if necessary. 


Solution



In order to prevent a deduplication folder or appliance from getting filled up with expired media, the Media Management routines in Backup Exec have been updated to proactively erase media in a deduplication folder that has reached its media overwrite date as follows:

1.  When a media mount operation occurs on a deduplication device, Backup Exec searches for media that has reached its expiration date, but is not in the scratch media pool.  If such media is found in the target deduplication folder, it is mounted, erased, and placed into the scratch media pool.

2.  While this is happening, the job will be in the "Queued" state.  Bringing up SGMon logging for Backup Exec (Tools -> Support Utilities -> Run the Debug Monitor for active debugging) will show that BE is sequentially mounting, erasing, and dismounting media.  This process can take a very long time if there are many media in this state.  This will be particularly noticeable to customers with existing deduplication folders or appliances who have either just installed Hotfix 154003, or have just upgraded to R3.

3.  Once the backlog of expired media has been moved to scratch, this pro-active erasing of media should reach a steady state in which only a few media at a time reach the expired state and need to be erased prior to the start of a backup operation.
 

Link for Hotfix 154003: http://www.symantec.com/docs/TECH154003

Temporarily disabling this feature

Customers who have a significant number of media in the expired state may need to temporarily work around the problem of having the expired media proactively erased.  To do this:
 

Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry. Registry modifications should only be carried-out by persons experienced in the use of the registry editor application. It is recommended that a complete backup of the registry and workstation be made prior to making any registry changes.

  1. Using the regedit tool, edit the following key:
    • Key Name: HKEY_LOCAL__MACHINE\SOFTWARE\Symantec\Backup Exec for Windows\Adamm
    • DWORD: Enable OST Space Reclamation
    • Value: 0
  2. Run the jobs that need to be run.
  3. Change the value of the Enable OST Space Reclamation DWORD to 1 to enable it again.
  4. Restart the BE services.
When there is a time where backups are typically not being performed, run a dummy backup to the deduplication device so that Backup Exec will proactively erase expired media during this down time for the backup system.
 
An alternate method to resolve this problem is to increase the length of the protection periods for the media sets containing the expired media.  This will reduce the number of expired media that need to be erased.  Then, over time, reduce the overwrite protection periods back to their original settings.




Article URL http://www.symantec.com/docs/TECH159843


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