Today I was testing an upgrade from Windows Server 2012 to Windows Server 2012 R2, for our Windows File Servers.
I tested two WS2012 File Servers, with iSCSI disks in a Failover Cluster. I upgraded each node in the cluster individually and had to take the node out of the cluster. After the upgrade I found that I couldn’t add the node to the Failover Cluster anymore.
At this point I decided to create the cluster again, and destroyed the ‘old’ cluster via the Failover Cluster Manager. I hoped (my mistake), that the connected disks would be released again. For one of the three disks, this was the case. I created the cluster again, but couldn’t add the iSCSI disks.
The disk could be found, but apparently it was still assigned or in use by the previous cluster.
After some digging I found the PowerShell command:
This seemed to be the solution and I could add the disk again.
I recommend running chkdsk on the disk afterwards.