We have two kinds of backups, for two kinds of threats:
- online. These are daily incrementals, done automatically via cron. It uses rsnapshot to save space when a file hasn’t changed. This protects us from accidental file deletion, since we can easily restore someone’s file from backups. It also gives us a window into when a file was created, if there’s some question about when a student did some work, for example. This backup is good because it’s completely automatic, so we’ll be sure it happens. It’s vulnerable to intentional damage.
- offline. These are full backups, done when we remember to do so. They’re kept in a disk that can be physically removed from the machine, or at least in an external disk cage that is powered off. This protects us from intentional damage, since not even the most talented hacker can destroy data in a disk that’s powered off. The disadvantage is that we have to remember to do the backups.
We’ve been buying drives such as the Seagate Barracuda 7200.14 ST3000DM001 3TB 7200 RPM 64 MB cache ($134 at newegg).
The most recent disks:
disk T: Seagate drive purchased Spring 2012. an offline backup. Last backed up 5/17/2013
disk U: Seagate drive purchased Spring 2012. an offline backup. Last backed up 5/23/2013
disk V: retired. has all daily incrementals from 5/22/2012 to 5/22/2013, the date it started getting hardware errors and turned into a read-only device. (Amazing coincidence that it failed after exactly a year of service.
disk X: new Seagate drive purchased April 2013. not currently in use. We’ll use this for performance testing these drives.
disk Y: new Seagate drive purchased April 2013. currently the drive for daily incrementals.
Each summer, we should retire one of the offline backup drives, for long-term retention, and then delete student accounts and such.
In the long run, we probably need more space for daily incrementals (so that we can back up the NAS, too) and have more reliable drives, such as a RAID 1 system, so that we don’t have to worry about drives failing like drive V just did.