A question that pops up on the VMTN Community once every day is what size VMFS datastore should I create? The answer always varies, one says “500Gb” the other says “1TB”. Now the real answer should be, it depends.
Most companies can use a simple formula in my opinion. First you should answer these questions:
- What’s the maximum amount of VMs you’ve set for a VMFS volume?
- What’s the average size of a VM in your environment? (First remove the really large VM’s that typically get an RDM.)
If you don’t know what the maximum amount of VMs should be just use a safe number, anywhere between 10 and 15. Here’s the formula I always use:
round((maxVMs * avgSize) + 20% )
I usually use increments of 25GB. This is where the round comes in to play. If you end up with 380GB round it up to 400GB and if you end up with 321GB round it up to 325GB. Let’s assume your average VM size is 30GB and your max amount of VMs per VMFS volume is 10:
(10*30) + 60 =360
360 rounded up -> 375GB