> From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
> boun...@opensolaris.org] On Behalf Of Kalle Anka
> Assume we have 100 disks in one zpool. Assume it takes 5 hours to scrub
> disk. If I scrub the zpool, how long time will it take?
> Will it scrub one disk at a time, so it will take 500 hours, i.e. in
sequence, just
> serial? Or is it possible to run the scrub in parallel, so it takes 5h no
> how many disks?

It will be approximately parallel, because it's actually scrubbing only the
used blocks, and the order it scrubs in will be approximately the order they
were written, which was intentionally parallel.

Aside from that, your question doesn't really make sense, because you don't
just stick a bunch of disks in a pool.  You make a pool out of vdev's which
are made of storage devices (in this case, disks.)  The type and size of
vdev (raidz, raidzN, mirror, etc) will greatly affect the performance, as
well as your data usage patterns.

Scrubbing is an approximately random IOPS task.  Mirrors parallelize random
IO much better than raid.

The amount of time it takes to scrub or resilver is dependent both on the
amount of used data on the vdev, and the on-disk ordering.

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