zfs discuss - Nov 2008 - proper or best zpool command to use to resurrected a disk that has been temporarily disconnected

Consider the following scenario.  A disk that is part of
a zfs zpool and is also part of a mirror in that zpool
becomes disconnected.  Imagine that the disconnection
last minutes or hours or days.

Then imagine that the disk becomes reconnected, but,
in a manner where hot-plug event does not cause it
to come back online automatically.  (If it helps
for concreteness, let us say that the disk is
implemented as an iSCSI target provided by some
other host/system).

What is the proper (or best if there is more than one
way) zpool command to use to bring the disk back
such that zfs will incrementally resilver it
as necessary (using the Dirty Time Log or
whatever)?

The candidate commands would seem to be:

zpool online
    But not clear if this is a candidate because
seemingly it is the inverse of "offline", and
offline is said to be an explicit action.

zpool clear
    Will the act of clearing errors cause ZFS to
resume using the device, and to incrementally
resilver off of the Dirty Time Log?

zfs replace
    But the text of the manpage seems to say
that replace is alot like an attach followed
by a detach.  The manpage prose also treats
the case where the disk has literally been
replace, that is, by a completely different
disk; the manpage does not explicitly mention
the case where the disk is the exact same
physical disk.  So, seemingly, replace could
end up resilvering the entire disk, not using
the Dirty Time Log?

zfs scrub
    Not a good candidate because it will read
the entire disk (or more precisely, all blocks that
are reachable).

thanks,
Andy

-- 
Email:  Andrew.Hisgen at sun.com

>>>>> "ah" == Andrew Hisgen <Andrew.Hisgen at
Sun.COM> writes:
    ah> (If it helps for concreteness, let us say that the disk is
    ah> implemented as an iSCSI target

for me, iSCSI targets do come back online automatically.

then, they don''t resilver, or don''t resilver enough.

If they were gone for too long, after a few hours or days they get
marked FAULTED for cksum errors.

then I ''zpool clear'' them, and they resilver a little more.

then I ''zpool scrub'', and they finish resilvering.  Unless
there are
too many CKSUM errors---then they get marked FAULTED again, and I have
to start over.
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