Previously, discard commands (UNMAP SCSI commands) that were sent from the guest were ignored by qemu and were not passed on to the underlying storage. This meant that storage that was no longer in use could not be freed up. In this release, it is now possible to pass on discard commands to the underlying storage. A new property called Enable Discard was added to the Virtual Disk window. When selected, and if all the restrictions are met, discard commands that are sent from the guest will not be ignored by qemu and will be passed on to the underlying storage. The reported unused blocks in the underlying storage thinly provisioned LUNs will be marked as free, and the reported consumed space will be reduced.
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