Collocation of copy storage pools and active-data pools

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

Using collocation on copy storage pools and active-data pools requires special consideration.

Primary storage pools complete a different recovery role than the recovery role completed by copy storage pools and active-data pools. Normally you use primary storage pools (or active-data pools) to recover data to clients directly. In a disaster, when both clients and the server are lost, you might use offsite active-data pool volumes to recover data directly to clients and the copy storage pool volumes to recover the primary storage pools. The types of recovery scenarios that concern you the most helps you to determine whether to use collocation on your copy storage pools and active-data pools.

Collocation typically results in partially filled volumes when you collocate by node or by file space. (Partially filled volumes are less prevalent, however, 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 and active-data pools whose storage pool volumes are taken offsite immediately. If you use collocation for copy storage pools or active-data pools, you must decide among the following:

Taking more partially filled volumes offsite, which increases the reclamation activity when the reclamation threshold is lowered or reached. The rate of reclamation for volumes in an active-data pool is typically faster than the rate for volumes in other types of storage pools.
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.

With collocation disabled for a copy storage pool or an active-data pool, typically there will be only a few partially filled volumes after data is backed up to the copy storage pool or copied to the active-data pool.

Consider your options carefully before you use collocation for copy storage pools and active-data pools, and whether to use simultaneous write. When not using simultaneous write, if you use collocation for your primary storage pools, you might want to disable collocation for copy storage pools and active-data pools. Collocation on copy storage pools or active-data 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 collocate settings are identical for the primary storage pools, active-data pools, and copy storage pools.