Every piece of data on disk is mirrored using RAID-1. This means that for each disk drive, there is another drive of the same size copying everything the first drive is doing. Every single modification to disk is simultaneously performed on a backup disk. If one of those disks fails, the other one is still running to keep things going smoothly. On our server, there are five physical drives, behaving as two logical drives plus a backup container.

Every three days, we do an incremental backup from the mirrored disk set to the spare container. Monthly, we do a full backup of the system. This provides additional security, because if both drives in one disk set fail (rare!), the other will still be there with a recent backup. This is also helpful because accidentally deleted files can sometimes be recovered if they existed for more than a few days (though you shouldn't rely on this!).

Periodically, we take all of the online backups and archive them to DVD. This is a rather involved process, since the backups are about 25 GB, compressed, so it doesn't happen as often as we'd like.

We also pay strict attention to security. Routine security audits are run frequently, unnecessary services are disabled, software patches are applied, and file permissions are checked often. The server itself is stored in a locked room with limited access. We hope to continue our excellent security record, and we can, with your help. (See Section 3.4.1, “Choosing a password”.)