# UNMAP Capability Feature

The UNMAP capability feature is a SCSI command (not a vSphere 5 feature) used with thin provisioned storage arrays as a way to reclaim space from disk blocks that have been written to after the data that resides on those disk blocks has been marked as deleted by an application or operating system. The UNMAP feature serves as the mechanism used by the Space Reclamation feature in vSphere 5 to reclaim space left by deleted data.

With thin provisioning, after data has been marked as deleted that space is still allocated by the storage array because it is not aware that the data has been deleted which results in inefficient space usage. The UNMAP feature allows an application or OS to tell the storage array that the disk blocks contain deleted data so the array can deallocate the blocks, reducing the amount of space allocated or in use on the array. This function allows thin provisioning to clean-up after itself and greatly increases the value and effectiveness of thin provisioning.

- UNMAP Capability Feature Behavior
- UNMAP Feature Support

Parent topic: Configuration