From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx04.extmail.prod.ext.phx2.redhat.com [10.5.110.8]) by int-mx08.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id n8HFYTeg031261 for ; Thu, 17 Sep 2009 11:34:29 -0400 Received: from server.klug.on.ca (server.klug.on.ca [205.189.48.131]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id n8HFYHPv016741 for ; Thu, 17 Sep 2009 11:34:18 -0400 Received: from linux.interlinx.bc.ca (d67-193-217-194.home3.cgocable.net [67.193.217.194]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by server.klug.on.ca (Postfix) with ESMTP id 23FFF2806 for ; Thu, 17 Sep 2009 11:34:17 -0400 (EDT) Received: from [IPv6:2001:4978:161:0:218:f3ff:fee1:65cc] (pc.interlinx.bc.ca [IPv6:2001:4978:161:0:218:f3ff:fee1:65cc]) by linux.interlinx.bc.ca (Postfix) with ESMTP id 912838721 for ; Thu, 17 Sep 2009 11:34:15 -0400 (EDT) Subject: Re: [linux-lvm] Using LVM Mirroring to obtain a usable backup From: "Brian J. Murrell" In-Reply-To: References: <1253109566.5326.15.camel@delo.gdit> <20090916181947.GB15438@us.ibm.com> <1253127828.3243.1.camel@delo.gdit> <1253181956.30299.25.camel@breeves.fab.redhat.com> Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-IQtHuraAqGlzeqjoBp7D" Date: Thu, 17 Sep 2009 11:34:14 -0400 Message-Id: <1253201655.2339.178.camel@pc.interlinx.bc.ca> Mime-Version: 1.0 Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: To: LVM general discussion and development --=-IQtHuraAqGlzeqjoBp7D Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Thu, 2009-09-17 at 11:06 -0400, Stuart D. Gathman wrote: > Using dd from a snapshot does not help the OP. Right. > He says the dd will take > 5-6 hours, and he needs a backup of the system *just before* the upgrade, > not hours before. Which a snapshot will achieve. > The rollback also needs to be quick. Which a snapshot will achieve. > A snapshot with dd does the "instant" backup part ok, but rollback > requires 5-6 hours to copy the snapsnot to a normal LV. Why would you copy the snapshot anywhere? If you decided you needed a roll-back, you boot from the snapshot of the root filesystem and have the /etc/fstab in that snapshot mount any snapshots of other filesystems he might have made. Personally, I keep separate /, /usr, and /var and so snapshot them all before an upgrade and fix up the /etc/fstab in the snapshot-of-/ to mount the /usr and /var snapshots (rather than the origins). AFAICT, the only issue the OP has with snapshots is that he fears an upgrade might screw up his LVM configuration. Personally, I think that is a low-probability fear, but everyone has to have their own comfort level I guess. > The OP is correct that creating and breaking a RAID1 mirror does what > he needs. Indeed. > I always build my VGs on md* devices. I typically have not. I typically don't mirror anything except my backup volume, which fully (as in bare metal restore able) backs up every filesystem I have in my network. For that reason I feel that mirroring the disks in all the machines is overkill. But granted, building systems on broken mirrors is easy enough and allows one the flexibility of mirroring at a later date if one wants. In fact I always thought/felt, that given that the MD superblock is at the end of a device (or partition), shrinking the filesystem on a partition and then trying to create an MD mirror with that partition should be doable. Never tried though. b. --=-IQtHuraAqGlzeqjoBp7D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEABECAAYFAkqyVvYACgkQl3EQlGLyuXBRbwCeJcKZZYRQyYoCQ8y7r60HR3uz 9G4AnjCkLLHqCjKLkbLizueb8qLOOvEb =mgVY -----END PGP SIGNATURE----- --=-IQtHuraAqGlzeqjoBp7D--