>Some vendors call this (and thins like it) "Thin Provisioning", I'd say
>it is more "accurate communication between 'disk' and filesystem" about
>in use blocks.
In some cases, users of disks are charged by bytes in use; when not using
SCSI UNMAP, a set of disks used for a zpool will in the end be charged for
the whole reservation; this becomes costly when your standard usage is
much less than your peak usage.
Thin provisioning can now be used for zpools as long as the underlying
LUNs have support for SCSI UNMAP
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