Local Storage VMDK Size Best Practice

[sant0sk1]

Back when we were running VMware server, we were instructed to keep the virtual disks on our guests relatively small (approx. 20GB or less) and to simply add more disks to the VM when needed. The reason being because larger VMDKs were unweildy and often caused performance issues. I am wondering if there is a guideline such as this for ESXi.

I believe that with a SAN disk size becomes irrelevant because they're never actually being moved or anything, but with local storage we need to consider disk performance and backups. Any best practices for disk sizes?

[vmmeup]

You should keep the number of VM's per datastore to 16 or less. Because of this I always recommend a datastore size of 500Gb or less unless you have vm's that have large disk sizes. The real important number is no more that 16 vm's per datastore. If you have concerns about large unwieldy vmdk's you can always use RDM's or store the data on a NAS share.

Sid Smith - Don't forget to award points for correct and helpful answers.

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VCP, VTSP, CCNA, CCA(Xen Server), MCTS Hyper-V & SCVMM08

[sant0sk1]

Why the 16 VMs per datastore limit? So if you recommend 500GB datastore with 16 VMs than you are recommending approx 30GB virtual disk for each VM?

[AntonVZhbankov]

If you're using Windows guests, keep VMDK's as little as possible. When you need more space, vmdk can be expanded in couple of minutes, but shrinking vmdk is very painful process.

Keep OS boot disk apart from data, additional disk can be expanded without reboot.

If you need temporary space, do not expand disks, create new and delete after use.

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VMware vExpert '2009

http://blog.vadmin.ru

[vmmeup · Accepted solution]

Not exactly checkout this blog article I wrote it should give you some additional insight.

Sid Smith

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VCP, VTSP, CCNA, CCA(Xen Server), MCTS Hyper-V & SCVMM08

• Don't forget to award points for correct and helpful answers.

[francois_tiers]

The DataStore volume is important but the size of VMDK is also important.

[jasoncllsystems]

Best sizing for a single LUN (storage) in ESX is 300GB and maximum VMFS up to 256GB.

Read more:

Regards,

CLL SYSTEMS http://www.cllsystems.com

MALAYSIA VMWARE COMMUNITIES

http://www.malaysiavm.com

[vmmeup]

I curious as to where the 300GB number comes form? Granted less VM's are better but datastores that are too small creates other issues such as the overhead of more luns to manage within the environment. There is also more to consider when looking at the datastore sizes. Depending on how the storage array is configured and the disked are carved up it can become irrelevant on the san side as to how many vm's are on each LUN if they are reading and writing to the same spindles. There are still other factors such as the esx queues etc.....but I think 300GB is too small for a cap, 500Gb is a more realistic number with the sizes of the vms out there today.

Sid Smith

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VCP, VTSP, CCNA, CCA(Xen Server), MCTS Hyper-V & SCVMM08

Don't forget to award points for correct and helpful answers.

[uushaggy]

I can see some logic in the 300GB LUN with a maximum file size (VMDK not VMFS) of 256GB (which is the default).

I would keep someone from making a VMDK comsuming the whole disk and having no room for snaps!