Controlling when reclamation occurs for off-site volumes

If you send copy storage pool volumes off-site, you can control reclamation by adjusting the reclamation threshold.

About this task

Suppose you plan to make daily storage pool backups to a copy storage pool, then mark all new volumes in the copy storage pool as offsite and send them to the off-site storage location. This strategy works well with one consideration if you are using automatic reclamation (the reclamation threshold is less than 100%).

Each day's storage pool backups will create a number of new copy-storage pool volumes, the last one being only partially filled. If the percentage of empty space on this partially filled volume is higher than the reclaim percentage, this volume becomes eligible for reclamation as soon as you mark it off-site. The reclamation process would cause a new volume to be created with the same files on it. The volume you take off-site would then be empty according to the Tivoli® Storage Manager database. If you do not recognize what is happening, you could perpetuate this process by marking the new partially filled volume off-site.

One way to resolve this situation is to keep partially filled volumes on-site until they fill up. However, this would mean a small amount of your data would be without an off-site copy for another day.

If you send copy storage pool volumes off-site, it is recommended you control pool reclamation by using the default value of 100. This turns reclamation off for the copy storage pool. You can start reclamation processing at desired times by changing the reclamation threshold for the storage pool. To monitor off-site volume utilization and help you decide what reclamation threshold to use, enter the following command:

query volume * access=offsite format=detailed

Depending on your data expiration patterns, you may not need to do reclamation of off-site volumes each day. You may choose to perform off-site reclamation on a less frequent basis. For example, suppose you ship copy-storage pool volumes to and from your off-site storage location once a week. You can run reclamation for the copy-storage pool weekly, so that as off-site volumes become empty they are sent back for reuse.

When you do perform reclamation for off-site volumes, the following sequence is recommended:

Procedure

  1. Back up your primary-storage pools to copy-storage pools or copy the active data in primary-storage pools to active-data pools.
  2. Turn on reclamation for copy-storage pools and active-data pools by lowering the reclamation threshold for copy-storage pools below 100%. The default for active-data pools is 60.
  3. When reclamation processing completes, turn off reclamation by raising the reclamation thresholds to 100%.
  4. Mark any newly created copy-storage pool volumes and active-data pool volumes as off-site, and then move them to the off-site location.

Results

This sequence ensures that the files on the new copy-storage pool volumes and active-data pool volumes are sent off-site, and are not inadvertently kept on-site because of reclamation.