In Windows Server 2008R2 and beyond it has been possible to extend the system volume online and without needing to resort to third party tools which often required at least a reboot.

I’ve now used this feature many times, but yesterday I had an issue when extending the volume of a Windows Server 2012 system drive where it returned the horrible looking error below ‘The parameter is incorrect’.

This leaves you in a scenario where the Disk Management tool reports that the disk has been increased to the new size, but viewing the disk properties in Explorer shows it has not been increased.

Nicholas Schoonover has a post detailing the same issue and suggests fixing it by first shrinking the disk, then extending it again. There are also comments on that post which suggest that extending it further might also resolve it. I wasn’t particularly keen to try out either of those suggestions immediately so did a bit more research.

It turns out this has been an issue within Windows Server for sometime and this Microsoft KB article details how to resolve it with the Diskpart utility, essentially the disk partition has been increased, but not the file system size.

It’s as simple as

DISKPART> select volume #

where # is the number of the affected volume which can be found with list volume.

DISKPART> extend filesystem

Now the file system size should match the new partition size.