Refer to the following best practices for monitoring ZFS storage pools:
Make sure that pool usage is below 90% of pool capacity for best performance.
Note that the zpool list command does not count RAID-Z parity as used space, nor does it subtract it from the pool capacity. RAID-Z pool capacity might be below 90%, while being nearly full. Use the zfs list pool command to check. See Displaying ZFS File System Information.
Use the zpool scrub command on a regular basis to identify data integrity problems:
If you have consumer-quality drives, consider a weekly scrubbing schedule.
If you have datacenter-quality drives, consider a monthly scrubbing schedule.
You should also run a scrub prior to replacing devices to ensure that all devices are currently operational.
Use the zpool status command on a weekly basis to monitor pool and pool device status. Also use the fmdump or fmdump -eV command to determine if any device faults or errors have occurred.