How to Shrink a VMDK

Hey all,

Not often you have to shrink a VMDK file, expanding one is super easy, even on a live Virtual Machine. Shrinking one however, isn’t as straight forward.

This guy does a decent job giving a step by step tutorial, but you can soon realize you can do it even faster, and without cloning…

1)  Use his math to get the disk size you need to edit inside the vmdk:

The number highlighted above, under the heading #Extent description, after the letters RW, defines the size of the VMware virtual disk (VMDK).

this number – 83886080, and it’s calculated as follows:

40 GB = 40 * 1024 * 1024 * 1024 / 512 = 83886080

2) Only shrink VMDKs in which you know the end of the disk contains allocated blocks, do this in a test only, make sure you have backups.

Now instead of cloning, simply remove the disk from the vm, and re-attach it. watch it’s reattached size be smaller, and it matches, much like the source guys post.