saltnz
Contributor
Contributor

LUN size recomendation

Hello I was wondering if there is a rule of thumb about how large a LUN should be? We are currently using 200GB luns and not 100% sure why. And we are asking ourselves do we continue to add new LUNS or do we increase the ones we currently have?

I know there is a 256 LUN limit, but we are not going to get anywhere near it and 2TB maximum size, but is there any recomendation for performance. We seem to recall being told 200GB was the ideal size for performance, but our searches to verify that have cvome up empty.

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3 Replies
Troy_Clavell
Immortal
Immortal

our LUNs are usually between 500 - 600 GB with 2MB Block sizes.

Here's a couple other good examples

http://www.yellow-bricks.com/2009/06/23/vmfslun-size/

http://www.gabesvirtualworld.com/storage-how-to-size-your-luns/

jpdicicco
Hot Shot
Hot Shot

There is no hard-and-fast rule of sizing. I have heard from VMware folks, that 512GB is usually a pretty good size for a general purpose drive (Windows C: drive, linux '/', applications, light file-sharing). The idea being that about 8-12 VMs simultaneously accessing the LUN was ideal. That was on ESX 3.5.

It all comes down to performance, though. And that depends on a combination of usage patterns and your SAN infrastructure (adapters, switches, array controllers, disk confiugration and disks).

There are some rules of thumb to follow, though:

1. Keep your LUNs consistent sizes when it makes sense to ease storage management

2. Separate sequential and random access vmdks on separate disk groups/meta LUNs

3. Do not overload a LUN with "too many" VMDKs, as your performance will eventually suffer as your ratio of seeks to reads/writes increases

4. If you can, add VMDKs one-at-a-time, baselining performance as you go

5. Set RAID levels appropriately for the workload and data access type (more writes will be much better on RAID 1 / 10)

6. Be sure to keep an eye on the performance of all components of your SAN (adapters, switches, array controllers, and disks)



Happy virtualizing!

JP

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Happy virtualizing! JP Please consider awarding points to helpful or correct replies.
saltnz
Contributor
Contributor

Thanks to you both, just what i was after

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