Thinking about backups.

Thinking about backups.

I've got a 3TB RAID5 volume (three 1.5TB disks) that reads between 150-200MB/s, but only writes at 25-50MB/s.

I would like to have full backup capacity of all 3TB of data, but the question becomes "how"?

If we assume that the reason for the slow write speed to the software RAID 5 array stems from parity calculation, then it stands to reason that a RAID 0 array wouldn't suffer the same speed limitation. Additionally, a RAID 0 array of two 1.5TB disks would hit a 3TB volume size, as opposed to requiring a third disk as in RAID 5.

I'm considering having a second, weaker box run software RAID0, and do a nightly rsync from primary box to the backup box. A dedicated 1Gb/s link would facilitate the copy.

If a drive in the RAID0 array fails, I replace it, rebuild and re-run the backup. If a drive in the RAID5 array fails, I replace it and rebuild. If the rebuild kills a drive and the RAID5 fails, I've got a backup. Meanwhile, I've got an isolated power supply, reducing the number of single points of failure. I'm using fewer drives in the backup machine, reducing cost. I'm reusing older hardware for the backup machine, reducing cost.

Tricky part is figuring out offsite backups from there, but my data isn't that valuable yet.