We had a failure overnight, I don't know what caused it but all hosts (9 in total) went into a half failed state in that they weren't responding in vCenter but could be pinged. I couldn't restart the management agent from the console so was forced to restart them via iLO.
Once I got all hosts back up, we've been left with one single datastore showing as "Inaccessible" and nothing I seem to do will kick it back into life. I'm not overfly familiar with the logs but it appears to be timing out
VMKernal.log
cpu38:68195)LVM: 15061: Failed to open device naa.600c0ff0001e3c7457b0c45a01000000:1 : Timeout
The Datastore is located on an HP MSA 2040, other volumes from said SAN that are mounted on various ESX hosts elsewhere or Hyper-V Servers have remained up so I know the SAN itself is OK.
I've rebooted all hosts in the cluster (one by one) just to be sure they came up cleanly
The iSCSI targets for this volume all seem to show Active but I did try to remove the targets and re-add them successfully
I had a spare server that I've built from scratch that once I added the iSCSI targets displayed the Datastore in the same Inaccessible state