Sometimes your ZFS drives on your disk runs away with you.
Then you quickly need commands to see what ZFS disk is the busiest.
Try this:
ssh to NAS/server
iostat -zxc 5
That will show you busiest. Then when you have zd you can do this:
find /dev -ls | grep zd144
That will be actual VM ID
iostat flags:
-z: Suppresses lines where all statistics are zero (helps reduce noise).
-x: Shows extended statistics for each device (includes metrics like %util, await, svctm).
-c: Displays CPU usage statistics.
5: Repeats the output every 5 seconds.