I am working on setting up our vSphere 5 environment. With vSphere 5 you can go > the 2TB VMFS datastore size that you were capped at with in 4.x, etc. What size datastores are people using and whats a good way to determine the correct size?

My environment:

Hosts: I will be using 6 hosts (2 CPUS per w/ 6 cores per) = 72 cores. 192GB RAM per host = 1152GB RAM.


VNX5500 with 35TB storage. This is tiered so it has a mix of SSD, SAS, NLS drives.

I saw someone use a formula someplace that looked like this:

(disk pool capacity – 10% free space) / total processors = datastore size

Does that look right? I may setup different levels of pools on the VNX, maybe gold/silver/bronze (which would basically be aimed at a SLA). So using this formula I would have a gold pool of lets say 10TB.

So thats (10TB - 10%) = 9TB (9000) / 72 = 125 so is that 1.25TB per datastore? And I would end up with ~7 datastores on 10TBs of space? Since VMware is aiming at easier managment through few objects, being able to go over 2TB per VMFs 5 DS now this doesn't look right to me?

Any help at all sizing my datastores would be much appreciated.

  • 1
    don't think the issue is total size of the DS, its how many VM's and types of VMs that will be using a DS. – tony roth Mar 9 '12 at 19:34

Check your VAAI driver - for example 3par is still recommending 2TB LUNs to achieve the best performance!

  • not all arrays support vaai. – tony roth Mar 9 '12 at 19:36

I am going to be using the formula that I posted above to size my drives. With the speed of my VNX5500's drive the IO problems that I had in the past shouldn't be a problem. I will post what my final sizes were across 30TB of space when we carve later this week.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.