How much of a performance overhead is there for sub-volume automated tiering on SSDs?
Sub-volume automated tiering does trigger additional work to be performed by the storage system, whether SSDs or HDDs are involved. Although we haven’t yet tested the performance impact of sub-volume automated tiering on SSDs, there would be a significant number of writes that would occur during the scheduled data movement phase of sub-volume automated tiering, either because new data was being moved to the SSDs, or old data was being moved off the SSD, which would trigger flash media garbage collection.
There would be a performance impact, but it would be hard to predict without knowing a bit more about the particular SSDs and the tiering profile and policies.
This was first published in January 2012