I have a zpool where I have just replaced a failed disk, and started a resilvering to the new disk.
What I don't understand is, why
zpool status says it want to scan 129TB, when the size of the vdev is ~30TB. When I look at
iostat -nx 1 then I can see the 5 disks in the vdev are getting heavy reads, and the new disk equal heavy writes. So zfs doesn't scan all the data as it says.
# zpool status tank3 |head pool: tank3 state: ONLINE status: One or more devices is currently being resilvered. The pool will continue to function, possibly in a degraded state. action: Wait for the resilver to complete. scan: resilver in progress since Thu Apr 30 09:59:15 2015 61.2T scanned out of 129T at 3.03G/s, 6h23m to go 946G resilvered, 47.34% done
I would say that each vdev is independent of each other, so a resilver of one should not require any scan of the others. Why does zfs scan all used disk space when resilvering?