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List:       zfs-discuss
Subject:    [zfs-discuss] How to clear invisible, partially received snapshots?
From:       "Andrew Daugherity" <adaugherity () tamu ! edu>
Date:       2010-04-29 16:54:46
Message-ID: 4BD97386020000F20002DB5D () vprmail ! tamu ! edu
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I currently use zfs send/recv for onsite backups [1], and am configuring
it for replication to an offsite server as well.  I did an initial full
send, and then a series of incrementals to bring the offsite pool up to
date.

During one of these transfers, the offsite server hung, and I had to
power-cycle it.  It came back up just fine, except that the snapshot it
was receiving when it hung appeared to be both present and nonexistent,
depending on which command was run.

'zfs recv' complained that the target snapshot already existed, but it
did not show up in the output of 'zfs list', and 'zfs destroy' said it
did not exist.

I ran a scrub, which did not find any errors; nor did it solve the
problem.  I discovered some useful commands with zdb [2], and found more
info:

zdb -d showed the snapshot, with an unusual name:
Dataset backup/ims/%zfs-auto-snap_daily-2010-04-22-1900 [ZPL], ID 6325,
cr_txg 28137403, 2.62T, 123234 objects

As opposed to a normal snapshot: 
Dataset backup/ims@zfs-auto-snap_daily-2010-04-21-1900 [ZPL], ID 5132,
cr_txg 27472350, 2.61T, 123200 objects

I then attempted 
'zfs destroy backup/ims/%zfs-auto-snap_daily-2010-04-22-1900', but it
still said the dataset did not exist.

Finally I exported the pool, and after importing it, the snapshot was
gone, and I could receive the snapshot normally.

Is there a way to clear a "partial" snapshot without an export/import
cycle?


Thanks,

Andrew

[1]
http://mail.opensolaris.org/pipermail/zfs-discuss/2009-December/034554.html
[2] http://www.cuddletech.com/blog/pivot/entry.php?id=980

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