So, I ran out of space on system partition in one of my primary xen virtual machines. Yea, things like this happen quite often when I literally underestimate myself. Unlike Linux, in this case there’s no power of init which lets you expand an LVM or move a system partition to new disk even without going through any reboots. I guess Microsoft realised that its an important option Windows should have so they provided in Windows Server 2008 and Windows 7 under Disk Management with an on the fly ability to either shrink or expand a system volume. But still its a painful risky process in XP or Server 2003. I’m familiar with third party softwares that help in resizing the partitions including GParted but like always I like to follow vendor supported methodologies on production machines. And it was ‘diskpart’ here. Booting the system from a Server 2008 / Vista DVD’s recovery tools or from WinPE, you can use diskpart. But first things first – there are three requirements you must have before going ahead.

1. Free space should exist contiguous right after the system partition
2. That free space partition must be of ‘primary’ type and must not be a logical partition.
3. It should also be in ‘unallocated’ or deleted form without an existence of a ‘drive’ on it.

I had 10Gig C: and D: drive on a 20Gig of a disk. Added 10 more from XenCenter totalling into 30. As I needed a primary unallocated partition after C: drive so I had to use robocopy to backup the D: drive’s data into a network samba share, format and then split it into one primary and one extended partition.

Legends:

Red = Total system drive space before and after the expand
Blue = Total free space on disk before and after expand
Green = Commands issued.