Date: Mon, 05 Jun 2006 08:14:01 -0500 From: Eric Anderson <anderson@centtech.com> To: Avleen Vig <lists-freebsd@silverwraith.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Snapshot's causing access problems Message-ID: <44842E19.8020307@centtech.com> In-Reply-To: <20060604120713.GP3685@silverwraith.com> References: <20060604120713.GP3685@silverwraith.com>
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Avleen Vig wrote: > Is anyone else experiencing this? > > I'm finding that during times when a snapshot is being created for a > partition, all access of that partition hangs until the snapshot is > completed. > > On a large partition (180Gb, 66% used), this takes over 10 minutes for > me. > I've found that any time the partition (which is NFS mounted) is being > accessed when the snapshot creation starts, the creation seems to take > an even longer amount of time and sometimes isn't complete after 30 mins > when I reboot the box. > > The problem is also really bad when the background fsck is starting and > makes a snapshot first, which takes a lot of production time out a > server which just crashed that I'm trying to restore. > This is probably a known issue. I say probably because it sounds like the regular fs suspended state that the filesystem goes into when doing the snapshot. You didn't mention which FreeBSD version you were using, but many fixes have been made to recent 6-STABLE branches regarding filesystems, but none that will alleviate your problems. Have you tried burying your snapshot file down deeper in the directory tree, and changing the mode on the parent(s) to something only root could love? For instance: /.snap/2006/snapshotfile Where /.snap and /.snap/2006 are chmod 0700. I think that you might only see the locking/hanging if a process attempts to stat the snapshot file while it's being created. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------
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