Recommended size limit VMFS volume

[Brijn]

Hello,

I addded some disks to my SAN and will be creating a new VMFS volume. Is there any magic numbers that I should stay below. In my case I would be to create a VMFS of about 2T, do I need to split that or not?

Tx

Bas

[Troy_Clavell]

I think you may here anywhere from 400BG - 600GB for your LUNS. We typically deploy 500GB LUNs. Remember your block sizes as well.

1MB=256

2MB=512

4MB=1024

8MB=2048

[HSpeirs]

Bas,

As long as you keep the LUN under 2TB you'll be fine.If it goes over 2TB, you only see the part over 2TB - so a 2.01TB will show as 0.01TB

H.

[vcpguy]

Frankly, there is no magic number. You can create 2 TB Luns and use extent to get more size.

There are multiple factors to decide the Lun Size - Like kind of Array, Applications, Raid Level etc..

Please refer to this link - http://virtualgeek.typepad.com/virtual_geek/2009/03/vmfs-best-practices-and-counter-fud.html

[Lightbulb]

You may want to keep them smaller just to avoid putting to many eggs in one basket. At around 500-600GB you can fit 10 maybe 15 regular sized VMs (Try to leave at least 10% of the datastore unused) With a larger datastore you are likely to put more VMs on it and performance can be degraded. Of course there are exceptions and if you plan your storage right you can pack more VMs on a datastore, but a lot of folk tend to hover around 400GB-600GB, and they might know something

[Funtoosh]

IMHO : It depends upon what kind of storage you are using. So basically storage would be deciding factor for lun size. If you created 2TB of lun, you should be looking at how your 2TB of space spread across how many spindle . Regarding to block size it is nothing but how big file each individual block can hold. If the file size are big then go for big block size or else small block size is OK to use .This way you will not waste the space.

[Brijn]

Hello,

Thank you for all the replies! I wasn't looking at VMFS as a filesystem, more as a simple placeholder. That probably did not make much sense, and as with any filesystem there is a risk of corruption, so the "too many eggs in a basket" is very valid.

Blocksize is not really an issue, there is few files sitting on the VMFS that even wasting 100MB is nothing compared to total storage.

My "problem" is that I have one really large VM (a fileserver) that is around 1T, it probably means that I have one VMFS larger then my others, not a problem, just a bit "risky" if the big VM ever disappears. The 1T basket will end up holding more eggs.

How do people generally implement large fileserver disks, same as all other servers, inside a VMDK, or differently?

TX!

Bas

[NWhiley]

With big disks, you could go with RDM though 1TB is well within VMFS limits.

Search within VMware for RDM there are lots of articles.

[TomHowarth]

Again this will depend your desired performance needs, RDMs are faster as they have direct access to the disk/LUN and you can utilise things like storages snapshots to aid backups and rollback, alternatively a 1TB VMDK could easily backed up by a VMware aware backup program.

If you found this or any other answer useful please consider the use of the Helpful or correct buttons to award points

Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author for the upcoming book "VMware Virtual Infrastructure Security: Securing ESX and the Virtual Environment”.

[Troy_Clavell]

here's a good article worth checking out.

http://searchvmware.techtarget.com/tip/0,289483,sid179_gci1350469_mem1,00.html

[Funtoosh]

sorry I misunderstood your question. Yeah for big files it is better to present LUN directly to the VM's rather than through host.

As other suggested about RDM, I would go for it. I have 500GB SQL running as RDM on VM's and its has significant I/O different if I present lun to the host and then put my SQL files on it.

So I am quite confident about large file system with RDM.

[Brijn]

Hi all,

Thanks for all the usefull feedback.. I'll go with one larger VMFS for th large system and try to keep the rest in the 500-800G range

Bas