Wednesday, January 27, 2010

Fireproof backups

After the last three earthquakes in the Bay Area, I started thinking that developing code without backup in an house made entirely of wood was probably not the best idea in the world. I work from home since a long time but until last year I always committed my code in the central repository of my employer, so it was not really an issue. I use RAID10 for my development computer so losing a disk is not a problem, but I would still loose all the code I wrote during the last year if the house burns down.

I basically never delete anything - when my disks are full I just buy bigger disks and copy everything on them. The consequence is that I have currently 572Gb to backup, so that excludes doing remote backup - I used rsync.net in the past and they have a terrific service, but uploading 300Gb of compressed data is not an option here - and I do not want to save only a subset of the disks.

Doing a backup on an external disk was the only solution remaining, but the problem is still that if the house burn then the backup disk will also burn. I could have rented a safe box at my bank but having to exchange the disks each week was too much of a burden. The solution I choose was to put the backup disk in a fireproof safe installed in the house. Now the next problem is that the house can burn when I am doing the backup - which will be done each night, so that's more or less eight hours each day with an unprotected backup. One neat solution I found was a disk that was directly encased in a fireproof safe. The big advantage of this disk is that it is protected even during the backup. The problem is that I also wanted to be able to store my passport and other documents in it. So I found the perfect solution: A USB fireproof safe. I can now put a 1TB disk inside the safe, and use it without having to open and close the safe.

The next step was the backup itself. I wanted to use good old dump/restore but with only one partition containing everything I was not able to unmount it to do the backup and doing a backup on a live partition - even during the night - is not a good idea. And anyway with a full backup taking ten hours to complete that was not an option. The best solution I found was to use a LVM snapshot - you just create a snapshot of the partition to backup, then you backup the snapshot and can continue to use the main partition. Unfortunately I did not had LVM installed so I had to copy the whole partition on an external disk, change the partitions to support LVM and then copy back the whole external disk - it took twenty-four hours to do this, but it was worth it.

The last step was to install dump and configure it to do a full backup each Sunday and an incremental backup each other night. I used some of the scripts delivered in the dump package, with some modifications to adjust them to my needs.

Now I receive an email each morning with the result of the backup. The last thing remaining to do will be to try a full restore.

Updated 01/10/2011
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