>No tools, ZFS does it automaticaly when freeing blocks when the
>underlying device advertises the functionality.
>ZFS ZVOLs shared over COMSTAR advertise SCSI UNMAP as well.
If a system was running something older, e.g., Solaris 11; the "free"
blocks will not be marked such on the server even after the system
upgrades to Solaris 11.1.
There might be a way to force that by disabling compression and then
create a large file full with NULs and then remove that. But you need to
check first that this has some effect before you even try.
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