Triggering reclamation as part of IBM Spectrum Protect server storage pool migration

Question & Answer

Question

When doing server storage pool migration, the server seems to initiate reclamation processes first. What is the explanation?

Cause

A migration task reports messages as with the following example:

08/22/2016 01:00:29 ANR0984I Process 2703 for MIGRATION started in the BACKGROUND at 01:00:29 AM. (PROCESS: 2703)
08/22/2016 01:00:29 ANR1000I Migration process 2703 started for storage pool <POOLNAME> automatically, highMig=8, lowMig=3, duration=None. (PROCESS: 2703)
08/22/2016 01:00:29 ANR1040I Space reclamation started for volume <VOLUME>, storage pool <POOLNAME> (process number 2703). (PROCESS: 2703)
08/22/2016 01:00:29 ANR1044I Removable volume <VOLUME> is required for space reclamation. (PROCESS: 2703)
..
08/22/2016 01:16:03 ANR1041I Space reclamation ended for volume <VOLUME>. (PROCESS: 2703)

08/22/2016 01:19:28 ANR1100I Migration started for volume <VOLUME>, storage pool <POOLNAME> (process number 2703). (PROCESS: 2703)
08/22/2016 01:19:28 ANR1102I Removable volume <VOLUME> is required for migration. (PROCESS: 2703)
..
08/22/2016 02:12:46 ANR0986I Process 2703 for MIGRATION running in the BACKGROUND processed 118 items for a total of 258,630,135,521 bytes with a completion state of SUCCESS at 02:12:46 AM. (SESSION: 315726, PROCESS: 2703)

Why is it that reclamation seems to be part of a migration process?

Answer

Space reclamation is expected to be more efficient than storage pool migration. For example, if a 500GB capacity scratch volume contains 2GB of data, representing one segment of a 50GB file, reclamation can return 500GB of storage space to the pool by moving 2GB of data and returning the volume to scratch. To achieve the same result, migration would need to move 50GB of data.

If reclamation brings the storage pool below the migration threshold, the server can avoid performing any storage pool migration.

The space reclamation performed by a migration process behaves as a normal space reclamation operation. For example, volumes are chosen based upon the reclamation threshold of the pool in which they reside.

[{"Product":{"code":"SSEQVQ","label":"IBM Spectrum Protect"},"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Component":"Server","Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"Version Independent","Edition":"","Line of Business":{"code":"LOB26","label":"Storage"}}]

Product Synonym

TSM

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Document Information

Modified date:
17 June 2018

UID

swg21990503

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