If you have Fast / Autotiering enabled on ALL datastores then you would have a single storage tier I guess. However, I know companies who differentiate storage tiers also in terms of "availability" (replication) etc.
Hmmmm makes sense if doing replication but I'm still stuck with the problem of Bronze vm's gaining access to the higher level storage. Would the solution then be to not do FAST across all the storage? So for Gold do FAST enabled but limit the amount of lower and mid tier. Then Silver Less upper, more middle and some lower. With bronze just having the remaining lower end storage?
Depends on how your service levels are defined for the services you have already sold. Typically what I have seen are setups like the following:
Gold - 15k RPM - Replicated
Silver - 15k RPM - NON-Replicated
Bronze - 10k RPM - NON-Replicated
Gold - Auto-Tiering enabled Storage across 3 tiers (EFD + 15K RPM + SATA
Silver - Auto-Tiering enabled Storage across 2 Tiers (15K RPM + SATA)
Bronze - No Auto-Tiering just SATA Disks
Forgot to say, if you are using Fast-VP you can set up Virtual Pool Policies which basically define which tiers of disks your pool can hit etc.
That's the way I thought it would most likely work out.
Thanks for the advice Duncan!