IC94934: DELETION OF DEREFERENCED DEDUPLICATED CHUNKS IS NOT OPTIMAL UNDER HEAVY WORKLOADS

IBM Tivoli Storage Manager V6.3 Fix Pack 5 (6.3.5.000) Server Downloads

APAR status

• Closed as program error.

Error description

• Tivoli Storage Manager server deletion of deduplicated chunks
  may perform poorly or contend with other operations on the
  server. The dereferenced chunk processing works as follows:
  After a file is deleted, or expired, the server checks to see
  if any other files have links to the chunk(s) that are owned by
  the given file.  If other files have links to the chunk(s), the
  chunk(s) and the corresponding storage owned by the chunk(s),
  cannot be deleted. However, if the chunk(s) no longer have
  dependencies within the deduplication catalog, the chunk is then
  processed for deletion from the database and the assigned
  storage pool(s). This end-to-end process can take quite a bit
  of time and resources, including locking, which can cause
  several undesired symptoms:
  - Delay in storage pool space being freed after expiration,
    migration or reclamations.
  - Locking contention between dereferenced deletions and other
    server operations such as session backups, reclamation,
    expiration, etc...
  - Excessive growth of the database involving the dereferenced
    queue tables and the deduplication catalog
  Tivoli Storage Manager Versions Affected:
    Tivoli Storage Manger V6 servers
  Customer/L2 Diagnostics
  This performance degradation issue can be verified by issuing
  the SHOW DEDUPDELETEINFO command. If the
  "Number of chunks waiting in queue"
  shows a very high number, that does not drop to 0 over time,
  this APAR should be applied.
  Initial Impact: Medium
  Additional Keywords:
    TSM bfDerefQueueThread queues for bfDerefDeleteThread slow
    degraded dedupdelete deref
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All Tivoli Storage Manager server users.     *
  ****************************************************************
  * PROBLEM DESCRIPTION: See error description.                  *
  ****************************************************************
  * RECOMMENDATION: Apply fixing level when available. This      *
  *                 problem is currently projected to be fixed   *
  *                 in levels 6.3.4.200 and 6.3.5.               *
  *                 Note that this is subject to change at the   *
  *                 discretion of IBM.                           *
  ****************************************************************
  *
  

Problem conclusion

• This problem was fixed.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  TSM SERVER

• Fixed component ID

  5698ISMSV

Applicable component levels

• R63A PSY

     UP

• R63H PSY

     UP

• R63L PSY

     UP

• R63S PSY

     UP

• R63W PSY

     UP