Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have followed these steps to convert a .vmdk virtual disk from thick-provisioned to thin-provisioned, however, a 50GB disk with 30GB free is still taking up 50GB. vSphere is showing the disks as thin-provisioned.

Any ideas?

This is on an ESXi 5 hypervisor, Single SAN storage

share|improve this question
It may be free from the Client OS's filesystem perspective but ESXi doesn't know that, can you show us a screen grab of the actual storage usage data from the VSClient please. Also when you converted it did you move it to a new Datastore or leave it on the same one? – Chopper3 Sep 12 '12 at 10:48
Provisioned Storage: 59.05 GB, Not-shared Storage 57.03 GB, Used Storage 57.03 GB. I converted on the same SAN. Only have the one :( – dmckenna Sep 12 '12 at 10:52
Files on SAN Size and Name 65 SERVER01-2b7f20bd.hlog 4294967296 SERVER01-5addd220.vswp 53687091200 SERVER01-flat.vmdk 8684 SERVER01.nvram 651 SERVER01.vmdk 0 SERVER01.vmsd 3064 SERVER01.vmx 2925 SERVER01.vmxf 5368709120 SERVER01_1-flat.vmdk 650 SERVER01_1.vmdk 631773 vmware-1.log 467144 vmware-2.log 374306 vmware-3.log 202339 vmware-4.log 180424 vmware.log 52428800 vmx-SERVER01-1524486688-1.vswp – dmckenna Sep 12 '12 at 10:59
up vote 2 down vote accepted

Thanks for the extra data, what I think is that your OS's filesystem has 'grabbed'/allocated all of the blocks that make up the virtual disk rather than just leave it as 'white-space', so the thinning process has only one option which is to assume that it's real data and leave it as it is.

I know you say you only have one SAN but do you mean you only have one SAN-provided LUN/Datastore? if you can then get a second LUN presented to your host/s big enough to hold the VM (maybe a bit more), partition and format it via the VSClient as VMFS and try the Storage vMotion again via the VSClient, ensuring you've chosen 'thin'. There's a chance that this more thorough method may see the filesystem's unused space for what it is and reduce the size accordingly. Let us know how you get on. Oh and I just remembered, this will work if you copy the VM from the SAN LUN/Datastore to any local VMFS-formatted disk/s on the host too, you can always copy it back to the SAN whether it shrinks or not, this may save you the faff of adding the LUN.

share|improve this answer

I've seen this behaviour with NFS storage - the vmdk files are allocated at file level and are thin-provisioned at the SAN level, so hence they will appear as consuming the full allocation. If it's FCP or iSCSI storage and you are seeing this, perhaps Storage vMotion to local host disk and then back to the SAN so that new vmdks are created.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.