Date: Tue, 22 Jun 2004 13:38:42 -0400 From: Bill Moran <wmoran@potentialtech.com> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-questions@freebsd.org Subject: Re: [OT] Re: What's the best possible email failover solution Message-ID: <20040622133842.4e4eaa85.wmoran@potentialtech.com> In-Reply-To: <40D86B3F.6060302@mac.com> References: <20040621132006.2b1a296f.wmoran@potentialtech.com> <a22ff294040621115173bad2e0@mail.gmail.com> <20040621172520.3544d6fe.wmoran@potentialtech.com> <20040621214348.GB63857@happy-idiot-talk.infracaninophile.co.uk> <20040621175626.3e762448.wmoran@potentialtech.com> <40D76DA3.9090809@mac.com> <20040621204111.6e684d45.wmoran@potentialtech.com> <40D79FF9.20308@mac.com> <20040622084726.524bfa39.wmoran@potentialtech.com> <3016.217.162.71.141.1087911989.squirrel@serv04.inetworx.ch> <20040622100825.01f0b258.wmoran@potentialtech.com> <40D8458D.1060500@zonnet.nl> <20040622105555.72a08502.wmoran@potentialtech.com> <86llifzlim.fsf@borg.borderworlds.dk> <20040622114322.440de5ef.wmoran@potentialtech.com> <40D86B3F.6060302@mac.com>
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Chuck Swiger <cswiger@mac.com> wrote: > Bill Moran wrote: > > Christian Laursen <xi@borderworlds.dk> wrote: > >> If you are running FreeBSD 5, you should be able to make a filesystem snapshot > >> and rsync from there. > > > > I suppose I should have commented on that ;) > > > > We're not running FreeBSD 5 on these production machines yet ... but it's > > likely we will be soon, so I'm considering using snapshots. > > > > To my understanding, we still have to stop Cyrus while the snapshot is > > being created (to ensure consistency) but since a snapshot takes a lot > > less time than an rsync, this should be a big improvement. Once the > > snapshot is created, rsync can take as long as necessary. > > No, snapshots can be taken without significantly interrupting running > processes, although I'm not sure how long filesystem access gets blocked while > creating the snapshot. You could also detach a RAID-1 mirror of the data > (using vinum, ccd, whatever) and backup that, and then re-attach and resync > the mirror drive to the live volume. > > Both of these methods make taking a very current backup easy; they do not > provide live replication of the data, however. Sort of. The Cyrus docs recommend this, with the warning that "you can potentially have a couple of inconsistent mailboxes in the snapshot" Me, I'd rather risk 5 minutes of Cyrus being down in the middle of the night than risk an inconsistent backup. Knowing my luck, the inconsistent part would be the one folder that causes a big stir when it can't be restored. I figure, if a snapshot takes (let's say) 20 seconds to complete. You stop cyrus, take the snapshot, then restart Cyrus ... you can then take all the time you need to backup from the snapshot. You're looking at less than 5 minutes fo downtime. In our case, our customers are mostly regional, so doing this at 2:00 AM shouldn't disrupt much. -- Bill Moran Potential Technologies http://www.potentialtech.com
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