I have found this KB:
But per usual, the article makes some vague statements that ... I am not sure what to do with. Specifically in the section below it says : "Caution: You should successfully unmount the datastore using the documented method prior to completing the steps described below" - bu then the steps below are, in fact, the process for unmounting" !?!?!
What the heck - so do I just:
use the vsphere client to:
1)perform the unmount for each host (or can be done for all hosts at once from the datastores and clusters view), then
2)perform the "detach" operation for each host individually from the vsphere client (step 3 below)
3)unpresent the LUN using vendor-specific storage tools/consoles
4)rescan from all hosts using the vsphere client
Is this correct?
"Unmounting a LUN using the vSphere Client
To unmount a LUN from an ESXi 5.0 host using the vSphere Client:
- If the LUN is an RDM, skip to Step 2. Otherwise, in the Configuration tab of the ESXi host, click Storage. Right-click the datastore being removed, and click Unmount.
A Confirm Datastore Unmount window appears. When the prerequisite criteria have been passed, click OK.
Note: To unmount a datastore from multiple hosts, in the vSphere Client select Hosts and Clusters, Datastores and Datastore Clusters view (Ctrl+Shift+D). Perform the unmount task and select the appropriate hosts that should no longer access the datastore to be unmounted.
- Click the Devices view (under Configuration > Storage😞
- Right-click the NAA ID of the LUN (as noted above) and click Detach. A Confirm Device Unmount window is displayed. When the prerequisite criteria have been passed, click OK. Under the Operational State of the Device, the LUN is listed as Unmounted.
Note: The Detach function must be performed on a per-host basis and does not propagate to other hosts in vCenter Server. If a LUN is presented to an initiator group or storage group on the SAN, the Detach function must be performed on every host in that initiator group before unmapping the LUN from the group on the SAN. Failing to follow this step results in an all-paths-down (APD) state for those hosts in the storage group on which Detach was not performed for the LUN being unmapped.
- The LUN can now be unpresented from the SAN. For more information, contact your storage array vendor.
- Perform a rescan on all ESXi hosts which had visibility to the LUN. The device is automatically removed from the Storage Adapters.
When the device is detached, it stays in an unmounted state even if the device is represented (that is, the detached state is persistent). To bring the device back online, the device must be attached."