From: Dave Chinner <david@fromorbit.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: xfs@oss.sgi.com, aurfalien <aurfalien@gmail.com>
Subject: Re: LVM + XFS + external log + snapshots
Date: Mon, 24 Jun 2013 09:39:33 +1000 [thread overview]
Message-ID: <20130623233933.GF29376@dastard> (raw)
In-Reply-To: <51C783B7.2040502@sandeen.net>
On Sun, Jun 23, 2013 at 06:24:39PM -0500, Eric Sandeen wrote:
> On 6/23/13 5:55 PM, Dave Chinner wrote:
> > On Fri, Jun 21, 2013 at 10:30:31PM -0700, aurfalien wrote:
> >> Hi all,
> >>
> >> So I have an XFS file system within LVM which has an external log.
> >>
> >> My mount option in FSTAB is;
> >>
> >> /dev/vg_spock_data/lv_data /data xfs logdev=/dev/sdc1,nobarrier,logbufs=8,noatime,nodiratime 1 1
> >>
> >> All is well no issues and very fast.
> >>
> >> Now I'd like to snapshot this bad boy and then run rsnapshot to create a few days backup.
> >
> > You need to snapshot the log device as well.
> >
> > But that is problematic in that you need to snapshot it at the same
> > time you snapshot the data volume. Hence yo'd have to do:
> >
> > # xfs_freeze -f <filesystem>
> > # <snapshot data volume>
> > # <snapshot log volume>
> > # xfs_freeze -u <filesystem>
> >
> > And now you can mount the snapshot with:
> >
> > # mount /dev/vg_spock_data/datasnapshot /snapshot -o nouuid,ro,logdev=/dev/vg_spock_log/logsnapshot
> >
> > If you can't snapshot the log device, then you can't snapshot the
> > filesystem. Yet another reason for using internal logs...
>
> Hm, given that freezing the fs makes the log (almost) completely clean, I wonder
> if he could mount with /dev/zero (or a loopback 0-filled file) to get at the snapshot,
> especially since it's being mounted RO.
>
> Should be safe & consistent, no?
In theory. Never tried it myself.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2013-06-23 23:39 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-22 5:30 LVM + XFS + external log + snapshots aurfalien
2013-06-22 7:58 ` Stan Hoeppner
2013-06-22 21:13 ` aurfalien
2013-06-23 22:55 ` Dave Chinner
2013-06-23 23:24 ` Eric Sandeen
2013-06-23 23:39 ` Dave Chinner [this message]
2013-06-24 0:33 ` aurfalien
2013-06-24 0:44 ` aurfalien
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