I am on a holiday and catching up on some articles I had saved that I still wanted to read. I stumbled on an article about sizing VMFS volumes by Ravi Venkat (Pure Storage) on flash based arrays. I must say that Ravi has a couple of excellent arguments around the operational and architectural simplicity of these new types of arrays and I do strongly believe that indeed it makes the world a lot easier.
IOps requirements, indeed forget about them when you have thousands at your disposal… And indeed your raid penalty also doesn’t really matter anymore, especially as many of these new storage arrays also have new types of raid-levels. Great right?
Yes in most cases this is great news! One thing to watch out for though is the failure domain. Meaning that if you create a large 32TB volume with hundreds of virtual machines the impact would be huge if this volume for whatever reason blows up. Not only the impact of the failure itself but also the RTO aka “Recovery Time Objective” would be substantially longer. Yes the array might be lightning fast, but your will and probably are limited by your backup solution. How long will it take to restore those 32TBs? Have you ever done the math?
It isn’t too complicated to do the math, but I would strongly suggest to test it! When I was an admin we had a clearly defined RTO and RPO. We tested these every once in a while, and even though we were already using tapeless backups, it still took a long time to restore 2TB.
Nevertheless, I do feel that Ravi points out the “hidden value” of these types of storage architectures. Definitely something to take in to account when you are looking for new storage… I am wondering how many of you are already using flash based solutions, and how you do your sizing.