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Changing Thin to Thick disk and vice-versa

You can change the existing Virtual Hard disks (VMware based) from Thick to thin and vice-versa. This can be achieved by either using VMotion/SVMotion or command line tool called "vmkfstools". Using VMotion/SVMotion is required a valid license. Select “Migrate” and choose “Change Datastore” and select the Disk format.

If you don’t have a VMotion/SVMotion license, use the following command to achieve the same.

From Thick to Thin:

vmkfstools –i "Thickdisk.vmdk" -d thin "Thindisk.vmdk"

It will start to clone to virtual hard disk in Thin Provision method. After completed, you can attach this disk with VM and power it on. If all looks good, you can delete the original thick disk from the data store.

Use the following command to see real-time usage of thin disk:

du –h "Thindisk.vmdk"

You can notice the big difference of disk usage between of Thin and Thick format disks.

From Thin to Thick:

vmkfstools –i "Thindisk.vmdk" -d zeroedthick "Thindisk.vmdk"

It will start to clone the virtual disk in Thick method.

In both disk conversion, should have enough disk space to achieve it since it clones and converts.

Comments

Graham said…
Following a recent customer disaster I had to restore VMs from backup with Backup Exec 2010 that used the VMware Agents using the vStorage API.

VMDK restores were successful, but the VM's failed to start because the VMDK's were thin provisioned when backed up.

vmkfstools –i "Thindisk.vmdk" -d zeroedthick "Thindisk.vmdk"

...saved my ass. Shame Symantec don't mention that in their best practices...
Anonymous said…
Note that thin provisioned disks change to thick if moved to another datastore when cold migrated as of 4.x. 8 hours of conversions wasted...
Hi,

Would be good to get some info about how to connect to run vmkfstools to complete the guide :)

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