.Bl -tag -width Ds
.It Cm allocated
Amount of storage used within the pool.
+See
+.Sy fragmentation
+and
+.Sy free
+for more information.
.It Sy capacity
Percentage of pool space used.
This property can also be referred to by its shortened column name,
.Pc .
This space occurs when a LUN is dynamically expanded.
.It Sy fragmentation
-The amount of fragmentation in the pool.
+The amount of fragmentation in the pool. As the amount of space
+.Sy allocated
+increases, it becomes more difficult to locate
+.Sy free
+space. This may result in lower write performance compared to pools with more
+unfragmented free space.
.It Sy free
The amount of free space available in the pool.
+By contrast, the
+.Xr zfs 8
+.Sy available
+property describes how much new data can be written to ZFS filesystems/volumes.
+The zpool
+.Sy free
+property is not generally useful for this purpose, and can be substantially more than the zfs
+.Sy available
+space. This discrepancy is due to several factors, including raidz party; zfs
+reservation, quota, refreservation, and refquota properties; and space set aside by
+.Sy spa_slop_shift
+(see
+.Xr zfs-module-parameters 5
+for more information).
.It Sy freeing
After a file system or snapshot is destroyed, the space it was using is
returned to the pool asynchronously.