You can use the device options of the vSphere vmkfstools command to perform administrative task for physical storage devices.

Managing SCSI Reservations of LUNs

Use the vmkfstools command to reserve a SCSI LUN for exclusive use by the ESXi host. You can also release a reservation so that other hosts can access the LUN, and reset a reservation, forcing all reservations from the target to be released. 

-L|--lock [reserve|release|lunreset|targetreset|busreset|readkeys|readresv] device
Caution: Using the -L option can interrupt the operations of other servers on a SAN. Use the -L option only when troubleshooting clustering setups.

Unless advised by VMware, never use this option on a LUN hosting a VMFS volume.

You can specify the -L option in several ways:

  • -L reserve – Reserves the specified LUN. After the reservation, only the server that reserved that LUN can access it. If other servers attempt to access that LUN, a reservation error appears.
  • -L release – Releases the reservation on the specified LUN. Other servers can access the LUN again.
  • -L lunreset – Resets the specified LUN by clearing any reservation on the LUN and making the LUN available to all servers again. The reset does not affect any of the other LUNs on the device. If another LUN on the device is reserved, it remains reserved.
  • -L targetreset – Resets the entire target. The reset clears any reservations on all the LUNs associated with that target and makes the LUNs available to all servers again.
  • -L busreset – Resets all accessible targets on the bus. The reset clears any reservation on all the LUNs accessible through the bus and makes them available to all servers again.
  • -L readkeys – Reads the reservation keys registered with a LUN. Applies to SCSI-III persistent group reservation functionality.
  • -L readresv – Reads the reservation state on a LUN. Applies to SCSI-III persistent group reservation functionality.

When entering the device parameter, use the following format: 

/vmfs/devices/disks/disk_ID:P

Breaking Device Locks

Use the vmkfstools command to break the device lock on a particular partition. 

-B|--breaklock device

When entering the device parameter, use the following format: 

/vmfs/devices/disks/disk_ID:P

You can use this command when a host fails in the middle of a datastore operation, such as expand the datastore, add an extent, or resignature. When you run this command, make sure that no other host is holding the lock.