VMAX 20k, My customer has LUNs that are currently part of a FAST policy that uses 200GB SSD, 600GB 15K FC, and 2TB SATA. We want to change them to a policy that uses 200GB SSD, 300GB 15K, and 2TB SATA. Will the simple changing of the associated policy force FAST to move all of the data from the 600GB to the 300GB drives, or will the fact that the LUN was previously bound to the 600GB tier force us to perform a manual migration for all the blocks to move to 300GB?
Check the section "Reassociating a storage group to a new policy" section in the SE array controls CLI product guide.
There is a restriction relevant to your question...
"If the FAST policy contains VP Tiers, all of the thin devices in the storage group must be bound to any VP pool in a tier in the policy. None of the thin devices can be bound to a pool outside of the policy."
The process for you will be:
- Remove the SG from FAST
- Migrate the SG to the new pool (see "migrating to a thin pool" in the above document)