During a recent server maintenance window, I came up against the VMWare Storage Filters. Unfortunately I wasn’t aware of them at the time. What this left me with was a LUN that was listed as available unused storage for all ESXi Hosts in the Cluster but could not be added as an extent for an existing Datastore. I could not for the life of me figure this out at 7pm on a Friday.
Come Monday morning after a coffee and a bit of research I had solved my problem. VMWare storage filtering will filter out LUNS if that LUN is; already in use, referenced as an RDM or not available on all ESX Hosts. It was this last condition that made me wonder. I had rebuilt a sandbox ESXi host to ESX to make use of NetApp’s mbralign tools, but I had not reconnected it in vCenter. This host reference was left offline and moved outside of any clusters in vCenter. This lone offline ESXi host was what was blocking the clearly available LUN being listed as an available extent!
Morale of the story: anything registered in the vCenter will be in play, regardless of state or location of the object. More on Storage Filtering is available in the vSphere Online Library.