DisallowSnapshotLUN new name = Force-Mount

Today i was helping a co-worker solving a problem with a particular LUN that is a VMFS volume. He could see the LUN but it was not seen as a VMFS volume. I had a similar issue some times before and solved this with the settings in the ESX configuration tab => advanced options => LVM => EnableResignature and DisallowSnapshotLUN. But in ESX4 this disappeared!

After a search i found this:

Mounting and resignaturing using the vSphere Client
It is no longer necessary to handle snapshots via the CLI. Resignature and Force-Mount operations have full GUI support and vCenter Server does VMFS rescans on all hosts after a resignature operation. This functionality is now built into the Add Storage wizard in vSphere Client. Through the GUI, the Add Storage Wizard now displays the VMFS label. Therefore, if a device is not mounted, but it has a label associated with it, you can make the assumption that it is a snapshot, or to use ESX 4.x terminology, a Volume Copy. If you use the GUI to force-mount a VMFS volume, it makes it a persistent mount which remains in place through reboots of the ESX host. vCenter Server does not allow this volume to be resignatured.

Prior to ESX 4.0
Historically, the EnableResignature and DisallowSnapshotLUN were applied server wide and applied to all volumes on an ESX. The new Resignature and Force-Mount are volume specific. This offers much greater granularity in the handling of snapshots.

Changes in ESX 4.0
The handling of Snapshot LUNs has changed dramatically in ESX 4.x:
Resignature is equivalent to EnableResignature = 1 in ESX 3.x.
Force-Mount is equivalent to DisallowSnapshotLUN = 0 in ESX 3.x.
The advanced configuration options EnableResignature and DisallowSnapshotLUN have been replaced in ESX 4 with a new CLI utility:
•ESX 4.x and ESXi 4.x: esxcfg-volume
•RCLI: vicfg-volume
Mounting and resignaturing from the command line
The esxcfg-volume command can be used in this way:
•Execute the following command to list the volumes that are detected as snapshots:

# esxcfg-volume -l

•Execute the following command to mount the volume “Name” without performing a resignaturing of that volume (this volume will not be mounted when the ESX host is rebooted):

# esxcfg-volume -m “Name”

•Execute the following command to mount the volume “Name” without performing a resignaturing of that volume (this volume will be mounted when the ESX host is rebooted):

# esxcfg-volume -M “Name”

•Execute the following command to resignature the volume “Name” (the volume will be mounted immediately after the resignature):

# esxcfg-volume -r “Name”
For more detailed information, see Managing Duplicate VMFS Datastores in the ESX Configuration Guide.

Hope it helps you!

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