Date: Tue, 28 Aug 2012 08:20:43 +0200 From: Guido Falsi <mad@madpilot.net> To: Matthew Seaman <matthew@FreeBSD.org> Cc: freebsd-fs@FreeBSD.org Subject: Re: ZFS snapshot Folder Disappearing Message-ID: <503C633B.2070508@madpilot.net> In-Reply-To: <503C5F2A.701@FreeBSD.org> References: <CAG27QgQdnQftnuk3o1ehD1W=0_ABsfu1KOsjxY%2Bc8B6iasSMdQ@mail.gmail.com> <CAM-i3ihGpwYZcYWuwxu8qk-3yASKQUE0hCmd4Dx%2BbWOoO9Yeog@mail.gmail.com> <CAG27QgT=yEv-BGFaqA79Bz5g9LLhMQwJKcNTDOt-=yESD5jCUA@mail.gmail.com> <503C5F2A.701@FreeBSD.org>
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On 08/28/12 08:03, Matthew Seaman wrote: > On 28/08/2012 00:33, Tim Gustafson wrote: >>> Did you try "zfs set snapdir=visible <pool/dataset>" ? >> >> I did not, but I never set them to be invisible either, and also when I did: >> >> ls -al /tank/export/projects/www/.zfs >> >> I saw a "snapshot" folder listed there; it was only when I tried: >> >> ls -al /tank/export/projects/www/.zfs/snapshot >> >> that I got the "Not a directory" message. > > I got bitten by this. It seemed to be triggered by cvsup'ing the Ports > CVS repo -- ever since the switch to SVN it hasn't bothered me at all. > > Anyhow, to the point: I first noticed this on a zpool which was built > under 8.1 originally, and had since tracked 8-STABLE and then 9-STABLE. > I tried a bunch of things to see if I could make the problem go away, > including the nuclear option: splitting the mirror, wiping one of the > drives, building a whole new zpool on it, using send..recv to move the > data over, reboot onto the new zpool, wipe original disk then add it to > the new zpool as the other half of a mirror. > > Didn't work. Whatever the problem is, I believe it is still present in > the latest ZFS code. (Can't say for sure because like I said, I'm > simply not running the sort of IO patterns that would trigger the > problem any more.) > > There's a PR for this somewhere (not created by me), but I can't find it > in my records right now. > http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/156781 I got hit by this a few times too. Ti me it looks like it's easier to get this problem on more low spec machines(low spec regarding ZFS, so anything under 3-4 GiB ram is on the low side, for example). Using nullfs across snapshots did trigger this easily. I did that to have a nullfs mounted snapshot of the whole filesystem structure. I'm using read only zfs clones for that now. -- Guido Falsi <mad@madpilot.net>
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