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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.

SAN:

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.

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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

2 Answers 2

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

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not all arrays support vaai. –  tony roth Mar 9 '12 at 19:36
up vote 0 down vote accepted

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.

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