MSA1000 LUN extended, do I need to do anything to extend vmfs?

[alistair_nelson]

I've searched the forums but am still unsure.

I've got two ESX 3 servers attached to an MSA1000. In the MSA1000 is a single LUN which I've just extended from 550GB to 700GB.

This process is still executing, but I'm unsure if I need to extend the VMFS as well?

vmkfstools -Z option talks about adding a new extent or partition, but all I've done is increases an existing LUN?

[davidbarclay]

You can't extend VMFS. You can add an extent, but generally not recommended.

Dave

[davidbarclay]

I should mention, it is (arguably) better to have many mid sized LUNs than one big one.

My rules are;

\- one vmfs per lun per disk group

\- no more than 30 vmdks per vmfs

Dave

[davidbarclay · Accepted solution]

So in your situation, I recommend you shrink the LUN back to the original 550 (if you can), then create a fresh LUN and format as VMFS.

If you are happy to have a second VMFS (my recommendation), then you are done. If you are not, you can add the new LUN as an extent on your original VMFS.

Make sense?

Dave

[alistair_nelson]

Thanks for the tip David. So, I do have less than 30 vmdk's so I only really need 1 VMFS according to your recommendations.

So my option is to either:

1) Shrink my LUN back to 550GB and add a new 150GB LUN and VMFS

or

2) Backup existing VM's, destroy and recreate VMFS offline

?

[davidbarclay]

Is the second LUN going to be on the same raid array? If so, there is little benefit making it a separate LUN (as they will contend for the same spindles). I say little, as there will still be some benefits due to LUN locking (when snapshots occur etc).

So, if you only have one raid array, backup destroy, recreate restore.

If it's new LUN on new raid array, create it new (larger than 150 if possible, but 150 is fine if its all you have).

Ultimately it depends on your environment. Typical vmdk sizes, i/o of the VMs etc etc.

Good luck.

Dave

[alistair_nelson]

Hi

So I have this working now.

The original Logical Volume on the MSA1000 was extended from 550GB to 700GB.

Next, using the VI Client, I added a new extent to the VMFS using all the newly available space from the logical volume.

This gave me a 700GB VMFS. Although it uses two extents, no downtime was required so it seems good for now.

David thanks very much for your assistance.

[davidbarclay]

No problems. Just remember that although a LUN failure won't break the whole VMFS (only the failed blocks) - you can't control where your vmdks live on the VMFS - so potentially if one of the LUNs fail or aren't reachable - the whole VMFS will fail.

Dave