ioztat is to OpenZFS datasets what
zpool-iostat(8) is to ZFS pools and vdevs.
zpool-iostat provides IO statistics for accesses to the lower level components
that make up a ZFS filesystem — the devices that underpin it and the mirrored, striped,
and parity-combined virtual devices these are part of —
ioztat does so for the filesystems
and virtual block devices layered on top.