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How much will the VM shrink?

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Shrinking a VM today is a time consuming process: zero out the free blocks, defrag, use vmware’s tools to shrink it partition by parition. I wanted a tool which would tell me after doing all that how much would it help. This turned out to be a complicated process as you have to find the free clusters in NTFS and find out whether they are actually allocated as in sparse VMDK files all blocks may not be allocated. I ran the tool on some VMs see below: Windows 2003, Windows NT & a couple of XP VMs.

fcp -f c:\work\vhd\w2k3.vhd
NTFS Free Sectors 594632
Free Sectors Allocated in Virtual Image 294496
Maximum Possible Saving by Shrinking 143 MB

fcp -f “c:\work\vm\w1\Windows XP Professional.vmdk”
NTFS Free Sectors 1049160
Free Sectors Allocated in Virtual Image 883144
Maximum Possible Saving by Shrinking 431 MB

fcp -f “c:\work\vhd\Windows XP Hard Disk.vhd”
NTFS Free Sectors 30124176
Free Sectors Allocated in Virtual Image 847013
Maximum Possible Saving by Shrinking 413 MB

fcp -f “c:\work\vm\wnta\wnta.vmdk”
NTFS Free Sectors 27724512
Free Sectors Allocated in Virtual Image 71656
Maximum Possible Saving by Shrinking 34 MB

I am thinking of releasing the tool, it only supports vmdk and vhd files today with NTFS file system. If you would like to get an early release, would be thrilled to share let me know.

Written by RS

December 31, 2008 at 8:21 am

One Response

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  1. […] machines – vmdk’s vhd’s, vdi’s, to recover free space and improve performance. Our offer to release a software tool to let you view how much storage you could recover has brought several responses from people who are […]


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