Wednesday, 27 July 2011

Extended Disks Remain Wrong Size

Whats wrong with this picture?


Spotted it yet?

Yes, that's right.  The Data (D:) Properties dialogue does not tie up with the details shown in Disk Management.  Disk Management shows the partition as 80GB where as the properties show it as only 10GB in capacity.

Ohh that's clever, how did you do that!?  ...well actually it isn't, but luckily enough for us dear reader, it's easy to fix.

How did I got into this predicament?  Simple:

  • Standard Windows 2008 VM, VMware ESXi, 4.1 Update 1
  • Didn't have enough datastore space during VM build, so built the VM with 10GB D:\ drive.  No problems there.
  • Had some storage added, created new datastore and Storage vMotioned the VM to new datastore, again all pretty standard stuff
  • Inside the VM, at the Windows 2008 level, I expanded the D:\ drive partition into extended 80Gb disk using Windows Disk Management.  Here is where we started having problems.
  • I received this oh so helpful error message during the partition expansion:

Thats how!

So, why? and - perhaps more importantly - what's this simple fix?

Why?  After some extensive Microsoft knowledge base bashing, I found this article:

KB832316 - The partition size is extended, but the file system remains the original size 
when you extend an NTFS volume

The stated cause being "This problem occurs because the NTFS driver exhausts its resources when it tries to extend the volume."

The KB also details how to fix.  But I'll include the four step fix that worked for me here too:

  • Open an administrative Command Prompt (Right click "Command Prompt" and select "Run as Administrator") and Run Diskpart
  • At the DISKPART> prompt, enter list volume 
  • select volume # (where # is the number of the incorrect volume) 
  • extend filesystem  
Now the file system size should match the extended partition size:

    Job done.

    - Chris

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