When changing the host ID of a LUN ESX will fail to mount the LUN and present the following message on the ESX host console:

"LVM: 4903: vmhba0:0:0:1 may be snapshot: disabling access. See resignaturing section in SAN config guide."

This is due to Logical Volume Management assuming that this is a snapshot LUN presented at a hardware level by the SAN.

To reset the LUN so it can be presented to ESX hosts:

- Ensure no ESX hosts are using/locking the LUN

In the Virtual Infrastructure Client:

- Select the ESX host
- Select the Configuration tab
- click on Advanced Settings
- Select LVM in the left pane
- Set LVM.EnableResignature to 1 and click OK
- Click Storage Adapters
- Click Rescan in the top right
- Click OK
- Click on Storage (SCSI, SAN and NFS)
- The volume should now appear as snapshot-xxx
- Right click and select Rename from the context menu
- click on Advanced Settings
- Select LVM in the left pane
- Set LVM.EnableResignature to 0 and click OK

On the remaining ESX hosts:

- Select the ESX host
- Select the Configuration tab
- Click Storage Adapters
- Click Rescan in the top right
- Click OK
- Click on Storage (SCSI, SAN and NFS)
- The volume should now appear

SAN Configuration Guide
http://www.vmware.com/pdf/vi3_esx_san_cfg.pdf

VMFS Volume Can Be Erroneously Recognized as a Snapshot
http://kb.vmware.com/kb/6482648