We have been trying to come up with some logic to both take size of the VMs and I/O into account. But we don’t have a set standard on LUN size anymore since the storage is now dedicated to our clusters, so we are also trying to come up with the best LUN size for each cluster individually.

I would love to see a script or spreadsheet where you could input 1) the known metrics (i.e. VM sizes & disk I/O for the past month) and 2) the known caps (i.e. Max VMs per LUN, & LUN size if you know it) and it would output the most efficient use of space taking into account disk I/O and map VMs to the LUNs. It would also be awesome if the tool could tell you what the most efficient LUN size would be based off your VM sizes if you didn’t already know it.

Another reason why we don’t have a set LUN size anymore is also because as our offering progresses more into production applications, users want more storage on the VM. So the average VM size on an older fully populated cluster and a newer cluster are drastically different. So we figured we would create a standard LUN size per cluster instead of an overall standard LUN size.

I don’t have the scripting skills to pull this one off, but it would make my life a lot easier during our huge storage migration project.

Thanks.

I deploy vm’s with from a .csv, from there i can choose the best place for each vm. Furthermore i make sure that the lun’s are balanced accross the hba’s.

Last Friday I was brainstorming with Gabrie van Zanten about the optimal placement of the VMDKs across our LUNs. We tried to come up with an algorithm that could give us insight in what would be our optimal storage layout.
First read the complete post …

I’m just interested in an algorythm that can sort this puzzle out.

Where are the geeks that can do the math?

Arnim

In addition to the considerations you mention I also do the following. Separate out any VMs that need attention to their storage design, eg and Exchange or SQL server. Often there may be multiple tiers of performance of underling storage, so the VMs and Datastores are categorised into the appropriate tiers. Lastly, consideration to keep some VMs disks away from each other, this is essentially like your IO limit but even though some may not break the metrics you may want them separate, for example different tiers in an application stack, development boxes etc.

Rodos

See this CapacityIQ link from VMworld2008 http://mylearn.vmware.com/courseware/25805/AD2398.pdf

You could script this with powershell indeed Alan. But it will be a lot, let me repeat this, a lot of work.

A couple of questions and remarks:
How often would you run this script?
How long do you think it would take to reshuffle your complete environment(?) let’s say a small environment of 4TB).
What about the scsi reservations/locks this reshuffling will trigger?
What’s the risk of moving vm’s around? (vs the benefits)

During the move around you would probably need an additional LUN which can be used as temporary storage for the VM’s that are moving around. You will need to move VMs off before you can start moving back in some and maybe even most cases. And the app / script would need to take diskspace in account during moving. (svmotion also uses snapshots for instance.)

I think it will be one gigantic puzzle. And especially for large environments it will be really really tough to get this done within off hours.

But than again, I wouldn’t be surprised if for instance EMC is working on a vStorage variant of this: http://virtualgeek.typepad.com/virtual_geek/2008/09/so-what-does-vs.html

As I said on Twitter, might be time to go NFS