Let’s say you are trying to extend a volume and you have the “Extend volume” option greyed out in Disk Management (MMC).Can you still extend the volume?Short answer: Yes.Is not really necessary to be in the exact same setup as I was to be able to apply the fix, but I am mentioning the full context to make sure you understand the reason why I introduced couple of additional steps.My setup: Microsoft Windows Server 2008 Enterprise + MSSQL cluster (5 instances) + SAN disks.1. Extend the LUN.2. Refresh the Disk Management MMC console and check if the additional disk space is available.Of course to be able to extend a volume is necessary to have the unallocated disk space to the right of the partitionvolume you wish to extend on the same drive.3. If the disk is part of a cluster, make sure you Turn On Maintenance Mode (Failover Cluster Management MMC - Storage). This action will not stop/affect the service who is using that disk (in my case will NOT affect my MSSQL instance – no downtime).
Turn On Maintenance Mode simply disables couple of disk checks the cluster service performs. If you don’t turn on maintenance mode, it is possible the cluster service to trigger a failover and this will move the disks (where you want to perform the extend) on the other cluster node.4. Use DISKPART to extend the Volume.DISKPART list diskDISKPART select disk 22DISKPART list partitionDIKSPART select partition 1DISKPART list volumeDISKPART select volume 17(I executed this command just to show how the volume selection should be done in case your partition has multiple volumes and the automatic default selected volume is not the one you intend to extend)DISKPART extend5. If the disk is part of a cluster, make sure you Turn Off Maintenance Mode (Failover Cluster Management MMC - Storage).
Extend Drive Option Grayed Out
Extend uses space to the right side of the partition. That is why it is greyed out.Now comes something that you will have to look out for. If you do manage to move the start of c drive into that un-allocated space your system may have issues with startup.If you had another OS installed you could use it to both move+extend the partition and fix your boot loader(it is in the system reserved partition.). You may also be able to fix it on another system the same way.A program called EasyBCD can edit the boot loader. You have to tell it to load one from another drive and give the system reserved partition a letter.It does take some work, but can be done.