LUN sizes?

[markuk]

Hi

We are going through another proof of concept for virtualization, so we are going to be using 3 servers to make up the pilot environment which will be connected to an EVA SAN.

What is the average size LUN you would present to the 3 servers?

I was thinking about presenting a 300GB LUN to start with, This would let us consolidate some of our smaller files servers.

Thanks

*<stron</p>

[microkid]

We always use 500GB LUN's, we found this an acceptable size which also performs quite good.

[demean0r]

It all depends on your needs, but for most LUNs we use 600 GB. This usually gives us room for 10-15 VMs per LUN.

[Ryan2]

+1 on both of the statements above. 500GB average LUN / Datastores. But I/O and individual VM sizing requirements should also be taken into account...

[COdlk]

We usually use 300GB LUNs. i think it really depends on what the VMs will be doing.

david

[TomHowarth]

What these results actually tell you is that you LUN sizes should be driven by you requirments and not a plucked out of the air figure.

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Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author for the upcoming book "[VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://my.safaribooksonline.com/9780136083214]”. Currently available on roughcuts

[TomHowarth]

What these results actually tell you is that you LUN sizes should be driven by you requirments and not a plucked out of the air figure.

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 vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://my.safaribooksonline.com/9780136083214]”. Currently available on roughcuts

[Prokein]

Not entirely sure how your answer is any helpful Tom. What "results" are you talking about?

LUN sizes can't actually be driven by requirements as there are plenty of folks who would appreciate LUNs larger than 500GB but don't/can't use them as the recommended size for VMFS is 500GB.

[demean0r]

I've never read anything from VMware stating the recommended LUN size is 500 GB. I've read from various experts to keep the number of VM's per VMFS volume between 15-20, but for high I/O VMs this number decreases, maybe dramatically.

[Prokein]

I was advised by the instructor of my VI3.5:IAC class, who is a senior VMware instructor not a 3rd party guy, that for performance reasons VMFS should be kept around 500GB. This was also the recommendation by a VMware storage group support engineer on an unrelated SR. It's true that VMware didn't put that into their best practices document (why? no idea), but I got it from two independant VMware sources, which makes it fairly credible to me.

Since you can't create more than one VMFS per LUN, the LUN size is thus "limited" to 500GB, even though you technically could take it up to 2GB.

[Rumple]

The actual determining factor isn't so much the actual size of the lun but the number of VM's on the LUN.

Recommendations are 10-15 VM's per LUN. Thats typically 2 vmdk's per VM...so potentially 30 VMDK files per LUN.

During snapshots you are causing a LUN level lock to occur which means every VM freezes for a split second during this time. (and during every 16MB growth of the snapshot file

If you have 10 VM's and they have 100GB disk files on them, size your LUN accordingly.

If you have VM's that are going to be heavily snapshotted (test VM's), then reduce the number of VM's (or do not put production class machines in the same LUN so that if there are performance problems, it's not going to matter as much.

The 10-15 number is what is important to remember as a guideline.

If you are using NFS, then forget all that and worry about your total IOPS available as nfs is a file level lock, not a LUN level. I've seen upwards of 80-100 VM's on a single NFS mount with no issues.

[acco014]

Basically it depends on your environmnet - by my suggestion is make use of 600GB - in future u dont find any difficulties

[TomHowarth · Accepted solution]

There is has never been a written figure for recommended LUN sizes from VMware. In good designs, the size of LUNs will be decided by proper capacity planning and sizing exercise, not a finger in the air number plucked from the sky a ball park starting point is (number of VM's per LUN * Size of VMDK) + 20%

this does not take into account any IOPS sizing etc

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 vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://my.safaribooksonline.com/9780136083214]”. Currently available on roughcuts

[markuk]

Thanks to every one for taking the time to reply.

Tom, I understand what you are saying at the moment it is only a pilot and we will be doing a proper capacity planning and sizing exercise.

Thanks again

Mark