How do I mirror two Macs as a backup scheme?
January 6, 2006 10:02 AM   Subscribe

I have two identical PowerMac G5s and a single copy of Mac OS X Server. One is a file server for small network. The other exists in case something happens to the first one. Through what mechanism can I keep the contents of these two systems in sync, whether constantly, every few hours, or nightly?

I have a bunch of harebrained schemes for how to do this, including simply using rsync on a schedule, Firewire mounting the backup server and duplicating the hard drive nightly, and simply keeping another IDE drive in the first server and using RAID to keep it as a duplicate and, if the primary server dies, just move the secondary drive over to the secondary server.

But surely others have dealt with this problem, and can suggest something more standard. Any suggestions?
posted by waldo to Computers & Internet (10 answers total)
Check out Foldershare. Microsoft owns it now and it is free and simple to setup. Mac OS version available and it works fine for me keeping folders on my laptop and mac mini at home in sync. It may not be industrial enough for you though.

Rsync works really well, and I've used it in the past for exactly what you are wanting. The -vau options are what I normally use. Tie that to a cron job and you can schedule it for whenever, but it only really works 1-way. Foldershare will work 2-way.
posted by nickerbocker at 10:34 AM on January 6, 2006

Foldershare has a limitation in that it only syncs files <2GB. Also, all the transfer information goes through Foldershare's server, but the file transfers are P2P. So if you are on the same network there shouldn't be any speed issues.
posted by nickerbocker at 10:37 AM on January 6, 2006

posted by schwa at 10:42 AM on January 6, 2006

Yes, rsync is the answer, though rsnapshot might be even better, since it automates the automation.
posted by tomierna at 10:54 AM on January 6, 2006

I would use both a 2-drive mirror RAID (with SoftRAID) and a nightly rsync backup.

- If a single drive fails, it recovers instantly and seamlessly.
- If another part of the machine fails, just move both of the hard drives.
- If the data gets erased from the RAID for any reason, you have the nightly backup.
posted by trevyn at 10:54 AM on January 6, 2006

Not rsync.

If you're using a mac, you'll need rsyncx, which is an implementation of rsync with HFS+ (Mac file system) support, so it'll copy over the different data forks that exists for HFS-stored files.

But yes, rsyncx plus cron is your friend. The first sync will be long and painful, but subsequent ones will be quick... I'd recommend an hourly sync.
posted by chota at 11:05 AM on January 6, 2006

rsync can also be set up to email the results daily - which I always find is nice for a little peace of mind.
posted by sixdifferentways at 11:06 AM on January 6, 2006

I'd recommend an hourly sync.

The disadvantage here is that if your data gets hosed, but not your server, you have to catch it and prevent the next sync within an average of 30 minutes.
posted by trevyn at 11:23 AM on January 6, 2006

Response by poster: I should mention that there's an existing backup system in place, involving a rotating roster of Firewire drives. The failover server will only be used in case of a serious hardware failure on the part of the primary server.
posted by waldo at 12:54 PM on January 6, 2006

If you're using a mac, you'll need rsyncx

Not if you're running OS X 10.4 or later. The -E option preserves HFS+ attributes.
posted by oaf at 5:24 PM on January 6, 2006

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