Collocation of copy storage pools

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Using collocation on copy storage pools requires special consideration. Collocation of copy storage pools, especially by node or file space, results in more partially filled volumes and potentially unnecessary offsite reclamation activity.

Primary storage pools play a different recovery role than copy storage pools. Normally, you use primary storage pools to recover data to clients directly. In a disaster, when both clients and the server are lost, you might use offsite copy storage pool volumes to recover the primary storage pools. The types of recovery scenarios can help you to determine whether to use collocation on your copy storage pools.

Collocation typically results in partially filled volumes when you collocate by node or by file space. However, partially filled volumes are less prevalent when you collocate by group. Partially filled volumes might be acceptable for primary storage pools because the volumes remain available and can be filled during the next migration process. However, partially filled volumes might be unacceptable for copy storage pools whose storage pool volumes are taken offsite immediately. If you use collocation for copy storage pools, you must make the following decisions:

Taking more partially filled volumes offsite, which increases the reclamation activity when the reclamation threshold is lowered or reached.
Leaving these partially filled volumes onsite until they fill and risk not having an offsite copy of the data on these volumes.
Whether to collocate by group to use as much tape capacity as possible.

When collocation is disabled for a copy storage pool, typically only a few partially filled volumes remain after data is backed up to the copy storage pool.

Consider your options carefully before you use collocation for copy storage pools, and whether to use simultaneous write. If you do not use simultaneous write and you use collocation for your primary storage pools, you might want to disable collocation for copy storage pools. Collocation of copy storage pools might be desirable if you have few clients with each of them having large amounts of incremental backup data each day. For collocation with simultaneous write, you must ensure that the collocation settings are identical for the primary storage pools and copy storage pools.