Comments on: How to Shrink a VMDK file in ESX

By: vmuserdude

vmuserdude — Sat, 07 Jan 2012 20:41:00 +0000

Ok, so I have a vm that has 100GB allocated to it. I’ve already shrunk the filesystem on the vm-os to 50GB, now I need to run the procedure you have here to reduce the size of the .vmdk as needed. Here’s the problem: the datastore only has about 781MB free. Will I be able to run the procedure in this article, or do I need to have 50GB free for the clone?

By: Villa Federico

Villa Federico — Tue, 06 Dec 2011 10:46:00 +0000

Nice shot man! It’s quite insane but when you have someone hanged by his balls this is very usefull!

By: Guest

Guest — Mon, 10 Oct 2011 21:28:00 +0000

This method works like a champ! Just be double-triple sure to resize the Guest OS partition smaller before starting this. I also rounded the partition size up by 0.1GB to allow for calculation variances, e.g., 20GB = 20.1GB. Don’t forget to multiply by 1024 to get from GB to MB to KB to B then divide by 512 to get the value. 20.1GB x 1024 = 20582.4MB x 1024 = 21076377.6KB X 1024 = 21582210662.4B / 512 = 42152755.2, round up to 42152756 (value to use in VMDK file. CP your VMDK file first in case you mess up with VI! Also, the ‘cold migrate’ method shown above moves the VMDK file and deletes the original, so if you mis-calcuated and corrupted your Guest OS then you are out of luck. The VMKFSTOOLS method is safer, just connect the cloned disk to the VM, that way if it doesn’t boot you can go back to the original VMDK file and descriptor (that you copied before modifying, remember?) **This information is provided “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.**

By: Daimus

Daimus — Tue, 23 Aug 2011 08:26:00 +0000

The procedure described is very dangerous, indeed. If you have not shrunk your partition within the operating system, you will be left with a corrupt filesystem. Any data that existed outside of the new extent size will be gone. Windows has a habit of scattering “immovable” system files well away from the start of the partition. If any of these file existed outside the extent, these will be lost and the system will most likely left unbootable.

Play it safe. Use Vmware converter to clone out to a new machine with your desired disk sizes. This is the only supported method of reducing the size of thick provisioned vDisks. If the operation fails, you still have your source VM to fall back on.

By: Moep

Moep — Tue, 31 May 2011 06:15:00 +0000

Online Storage vMotion made my Windows 2008 VM crash and then the vMotion failed. Offline works fine.

By: jas

jas — Thu, 26 May 2011 14:03:00 +0000

yes you are spot on about shrinking the filesystem. with win2k8 there is buildin tool in server management under storage | disk management, right click and shrink.. we shrinked the thick 40G to thin 12G.

By: jas

jas — Thu, 26 May 2011 14:00:00 +0000

Thanks for sharing, this works great!

By: professionalvmware

professionalvmware — Sun, 15 May 2011 19:48:00 +0000

The technique seemed to work fine. Did you happen to shrink the filesystem within the guest OS first?

“The reason for this probably stems from those few customers that were not familiar with using the command properly and ended up cutting off too much of the disk and corrupted their Guest OS file system as a result.”

Basically, from the sound of it, you chopped the end off your windows filesystem. Unfortunately there is not much I can do to help you out of that one. If you still have a copy of the VM or a good set of backups, try using gparted to shrink NTFS first, then use the above method to shrink the VMDK.

By: TofTof06

TofTof06 — Sat, 14 May 2011 22:23:00 +0000

Hi all
Been trying this on a Windows 2008 R2 VM on a vSphere 4.1.0 host but the VM refuses to start.
I was reducing a thick 40 Go vmdk to a thick 25 Go (only 10 Go used in the original VMDK).
I have changed the information in the descriptor file and used vSphere Client to cold migrate it to another VMFS datastore.
The destination file was indeed doing 25 Go but the result is : unable to load operating system.
Any idea to help me making this work in vSphere 4.1 are welcomed.
I don’t really want to import those VMs
Thanks for your help

By: Cgchen

Cgchen — Wed, 08 Dec 2010 04:12:00 +0000

my vmdk is 40gb but only 5gb was used so I tried to shrink it to 6gb (RW 12582912). The vmdk was cloned but grub bootloader failed to locate the boot partition (this is a linux VM)

Any idea why this is happening?