Not all data is accessed equally. Some data is more popular than other data that may only be accessed infrequently. With the introduction of FAST VP in the CX4 & VNX series it is possible to create a single storage pool that has multiple different types of drives. The system chops your LUNs into slices and each slice is assigned a temperature based on the activity of that slice. Heavy accessed slices are hot, infrequently accessed slices are cold. FAST VP then moves the hottest slices to the fastest tier. Once that tier is full the remaining hot slices go to the second fastest tier, etc… This does absolute wonders to your TCO: your cold data is now stored on cheap NL-SAS disks instead of expensive SSDs and your end-users won’t know a thing. There’s one scenario which will get you in trouble though and that’s infrequent, heavy use of formerly cold data…
auto tiering
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The last breakout session I attended at EMC World 2013 was titled “Leveraging SSD: Designing for FAST Cache & FAST VP on Unified Storage”. By far one of the best breakout sessions of the week for me: technical and I can apply it in the field on pretty much a daily basis!
If you’ve got SSD drives in a VNX you can use it in two ways: as FAST Cache or as an extreme performance tier in your storage pools (FAST VP). Either of these implementations has advantages and disadvantages and they can also be used concurrently (i.e. use FAST Cache AND FAST VP). It depends on what you want to do…
But let’s start at the beginning: first you need to figure out your skew! What?!