I often hear people making comments around Storage IO Control and Storage DRS IO Load Balancing being one and the same thing. It has been one of those myths that has been floating around for a long time now, and with this article I am going to try to stop it.
I guess where this myth comes from is that when you create a Datastore Cluster and you enable Storage DRS IO Load Balancing then it configures Storage IO Control for you automatically on all datastores which are part of that particular Datastore Cluster. This seems to give people the impression that they are the same thing.
I have heard people making these claims especially around interoperability discussions. For example, one of the common made mistakes is that you should not enable Storage IO Control on a datastore which has auto-tiering (like EMC FAST for instance) enabled. Now the thing is that in the Storage DRS Interop white paper it is listed that when using an auto-tiering array you should disable IO Load Balancing when using Storage DRS. However, let is be clear Storage IO Control and Storage DRS Load Balancing are not one and the same thing and Storage IO Control is supported in those scenarios!
Storage DRS uses Storage IO Control to retrieve the IO metrics required to create load balancing recommendations. So lets repeat that, Storage DRS leverages Storage IO Control. Storage IO Control works perfectly fine without Storage DRS. Storage IO Control is all about handling queues and limiting the impact of short IO spikes. Storage DRS is about sustained latency and moving virtual machines around to balance out the environment.
I guess I can summarize this article in just one sentence:
Storage IO Control != Storage DRS IO Load Balancing