want pool io kstats
zfs - Zettabyte File System
From Matt Ahrens's bug report at Delphix:
We want a io kstat, which can be consumed by iostat(1m), which tells us how much i/o is happening to each pool. This will essentially be an aggregate of the i/o to the underlying devices, but will include queueing that happens at the zfs (vdev_queue.c) level.