On 6/30/2014 6:28 PM, deoren wrote: > I'm still pretty new to running a mail server, but one thing I've come > to appreciate over the years is a good backup strategy. Since I have > always run my own servers for practice and for personal use I don't have > access to Enterprise backup solutions. Because of that I usually just > fall back to scripts and tarballs and offload the content on a regular > basis. >
LVM snapshots of the file system combined with rdiff-backup to a second server. The main advantages over tar/rsync: - Deltas instead of entire file. Plus deltas are compressed. - It handles lots and lots of files well. - You can easily age off older deltas. Not hard to keep 26W or 52W of daily or a few-times-per-day backups. - Metadata such as file permissions / owner / group are stored in regular files in the rdiff-backup target directory, so the destination file system where you store the rdiff-backup files does not matter much. - Files are stored along with a SHA1 hash, making it possible to detect bitrot in your backups. Downsides: - Restoring a file more then 10 or 20 deltas old requires a lot of disk activity (putting /tmp on a SSD helps a lot) Suggestions: - Each mailbox folder should be its own rdiff-backup target. That allows you to only backup mailbox folders which have changed in last N hours/days. It also means that if things go pear-shaped with rdiff-backup, only that one backup target is at risk. - Put /tmp on a SSD, especially if you run rdiff-backup "verify" and validate more then 1-2 revisions into the past. - Once you have your rdiff-backup directories on another server it is trivial to LVM snapshot that and then rsync to either a USB drive or offsite server (or both). The rdiff-backup directory structure is very rsync-friendly. - If you're going to do hourly backups, have (2) rdiff-backup locations. One that deals with the hourly backups and has a short retention cycle of only 3-4 weeks. Another location that deals with daily backups and has a 55W retention cycle. That way you can restore to an hour within the past 3-4 weeks, or any day within the past 55W.
