Understanding How ZFS Calculates Used Space
This document explains how ZFS calculates the amount of used space within a zpool and provides examples of how various ZFS features affect that calculation. DETAILS A ZFS storage pool is a logical collection of devices that provide space for datasets such as filesystems, snapshots and volumes. A zfs pool can be used as a filesystem, i.e. such as mounting/unmounting; to take snapshots that provides read-only (clones are writable copies of snapshots) copies of the filesystem taken in the past; to create volumes that can be accessed as a raw and a block device and for setting properties on datasets. Interaction of all these datasets and associated properties such as quotas, reservations, compression and deduplication (Solaris 11 only) play a role in how ZFS calculates space usage. Neither the du nor df command have been updated to account for ZFS file system space usage. When calculating zfs space usage, always use the following command. # zfs list -r -o space <pool_name...
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