ESXi 4 Thin Provisioning

[Sqwim]

Hi, we're considering stepping into the world of virtualisation and I'm currently evaluating ESXi 4 and vSphere (on just the one host at the moment with 400GB local SAS drives (RAID10)).

I have a VM configured for Thin Disk Provisioning. The Hard Disk settings show a 10GB currently provisioned size:

Yet the Resource Summary for this machine shows 11GB as being currently provisioned:

And, more annoyingly / importantly than the disparity above, if I try to copy a 1.8GB file to this machine it runs out of space. This raises two questions:

1) Why would it run out of space when 11 - 7.82 = 3.18GB is theoretically available?

2) Even if it did run out of space shouldn't the This Provisioning automatically allocate more space so this does not happen? As you can see there is plenty of space available in the datastore.

I'd very much appreciate any responses / advice that you can offer as despite reading plenty of VMWare guides I can;t fothom this one out.

Thanks

Sqwim

[AntonVZhbankov]

Do not forget that there is swap file with RAM size, so add 1GB

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VMware vExpert '2009

http://blog.vadmin.ru

[Sqwim]

True, but that would still have left enough space. Also, if Thin Provisioned the disks shoudl automaticaly have allocated more space shouldn't it?

[dab · Accepted solution]

How large is the Disk in Windows inside the VM? How much freespace do you have there?

Daniel

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[Sqwim]

The disk inside Windows is 12GB and has 1.3GB free. Disk Management shows 8GB allocated and 4GB unallocated.

Would this be the problem? Am I being naive to assume that VMWare Thin Disk Provisioning would, somehow, extend the virtual disk on the ESXi host and also the guest OS when more space is allocated via Thin Provisioning?

[dab]

Yes this is the Problem! The VMDK-Diskfile is just the "physical" or logical volume, not the OS partition.

Hopefully your OS is VISTA or w2k8, then you can use Diskpart / List Volume / Select Volume / Extend.

If the OS is XP or w2k3 you have to run a tool like "Server Magic" oder "Disk Director Server". If you don't own such a tool you can use Diskpart but you have to use it from booted Windows PE (Bart-PE).

You can't extend a Boot- or System-Partition direct from the booted OS before VISTA/w2k8.

ATTENTION: Before doing such a task please do a Full-Backup of your VM!

Daniel

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[Rumple]

Just as another note, if your system is XP or 2003, then you can shutdown the running system, attach its disk to another VM (I usually keep an XP desktop VM just for this purpose) and use the diskpart to extend out the disk that way. Just remember to remove that servers disk from the VM used to extend the disk afterwards.

Note: you do not need ot remove the Disk to be extended from the original server as long as you do not try to power it on while its attached to another system

[DSTAVERT]

Thin provisioning is not about expanding beyond the size you have assigned. It is about not pre allocating all the space. If you assign a disk of 50GB but the OS only takes up 10 GB then the thin provisioned disk would only be 10GB in size. Over time the disk could grow to a MAXIMUM of 50 GB.

[AntonVZhbankov]

You can extend partition without reboots and mounting disk to another VM.

Use Dell ExtPart (36kB size). It would take a couple of seconds only.

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VMware vExpert '2009

http://blog.vadmin.ru

[DSTAVERT]

Unless you have a lot invested in this I would start over. Decide on a reasonable size for your OS partition. Don't provision too much and rely on thin provisioning to keep it smaller. Use your basic best practices setting up your virtual machines. Don't assign more processor or ram than you need. Even though they are virtual treat them as you would any physical machine.

[Sqwim]

Thanks all for the answers and for highlighting my naivity! The VM in question was a Win2003 Svr so I've had a play with booting from Windows PE and using DISKPART to extend the volume and this has eventually worked.

You've certainly cleared up a few lack of Thin Provisioning understandings that I had. I've another, semi related disk provisioning question though (sorry!):

What determines whether you can change the Provisioned Size of a disk? As you can see here the option is greyed out:

Yet here the option is available:

I can't identify an reason for this. It's not Thin v Thick provisioned disks, it's not determined by the power state of the machine etc. I'm puzzled, if you can enlighten me I'd appreciate it.

Cheers

[DSTAVERT]

Once you create the disk it can't be changed from the GUI. It is possible from the command line (Unsupported console). I wouldn't mess with that unless you can't do something else. Create a new disk of the proper size.

[Sqwim]

Are you sure? It certainly seems to work. I've just changed 10GB disk provision pictured above to 16GB and the changes have been made:

When I check Disk Management inthe guest OS it is now showing 16GB:

[DSTAVERT]

You are right I was in a 3.5 forum and my mind hadn't switched over.

No matter what, I wouldn't change disk sizes even though it is possible, again, unless there is no option. On the physical disk where is that new chunk in relation to the original chunk?

[Sqwim]

True, there would likely be some fragmentation. But then that is a risk / performance issue with Thin Provisioning anyway isn't it?

I agree it's probably not ideal, and I'm beginning to form the opinion that thick disks with plenty of space is the way forward but I'm still curious as to what determines whether the provisioned storage can be changed or not? Anyone?

[Sqwim]

Just a quick update that I found the reason for provisioned size being greyed out. It is greyed out if the VM has any snapshots.

[KeithThomas]

I am a newbie ESX user, we are running nice new v4.0 software. Some of our virtual machines have the options to shrink disks greyed out (see screenshot) and others do not. We don't know why there is a difference.

This is a little frustrating as using older non-centralized tools (e.g. VMware Server) I don't seem to remember this being such an issue, shrinking was routine.

As you can see I have no snapshots.

[Tomas_Chmel]

Hi

It may be only wild guess, but the problem is probably in the fact, that the disk is created as IDE disk, and not SCSI.

[cincinnerdi]

@Tomas - I think you are correct.

A VM I was using had provisioned size grayed out, despite the fact that there were no snapshots. (Controller was IDE. Disk type was thick.)

I used Converter, changed the Devices-Disk controller from IDE to SCSI. This fixed the issue. I was then able to have GUI access to increase the disk size.

Thx for the "wild guess"!

keywords: vsphere grey gray disk size expand