Date: Wed, 9 Jun 2004 00:07:00 -0400 (EDT) From: Robert Watson <rwatson@freebsd.org> To: Randy Bush <randy@psg.com> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: snapshot dump hangs Message-ID: <Pine.NEB.3.96L.1040609000437.93490B-100000@fledge.watson.org> In-Reply-To: <16582.31631.362797.734568@ran.psg.com>
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On Tue, 8 Jun 2004, Randy Bush wrote: > i try to dump a live filesys with > > /sbin/rdump 0Luaf remote.sys:/backup/foo/var.dump /dev/twed0s1d > > the screen does > > DUMP: Connection to remote.sys established. > DUMP: Date of this level 0 dump: Wed Jun 9 01:52:32 2004 > DUMP: Date of last level 0 dump: the epoch > DUMP: Dumping snapshot of /dev/twed0s1d (/var) to /backup/foo/var.dump on host remote.sys > DUMP: mapping (Pass I) [regular files] > DUMP: mapping (Pass II) [directories] > DUMP: estimated 513616 tape blocks. > DUMP: dumping (Pass III) [directories] > DUMP: dumping (Pass IV) [regular files] > > and then just hangs forever > > there is nothing in /var/.snap dump unlinks the snapshot as soon as it opens it so that it will be GC'd when dump is done... > i can > > mount -u -o snapshot /var/.snap/snap1 /var And this doesn't hang, or does? > this is horrifyingly reproducable and happens with other source > filesystems. I'm using dump with -L regularly with a recent -CURRENT box at work for backups. On the whole, it's worked without problems, but I did once observe dump hanging, in the sbwait state (suggesting it's blocked on socket I/O?). At the time, I was unable to do much diagnosis. Could you do a couple of things: (1) Could you do a "ps awxl" and see what wait channel dump is blocked on? (2) Could you break into DDB and generate a stack trace for dump? (3) Could you run "show lockedvnods" in DDB and show the results? (4) Could you run "show locks <pid>" on the dump process? Thanks! Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Senior Research Scientist, McAfee Research
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