« on: November 15, 2012, 08:12:03 AM »
I think it is important to distinguish between data availability and data integrity, since some of this discussion is conflating these two principles. RAID, for example, provides data availability but it does not provide data integrity as does, for example, off site backups.
Think about it this way. If you build a mirrored pair of disks and copy all of your photographs to the raid set, you are still at risk of data loss; it is easy to accidentally delete a photograph and the raid set will not enable you to recover it because the data will be deleted from both disks.
If you want both data availability and data integrity then implement RAID (raid 1, raid 5, etc) *and* then off site backups (off site here defined as media that is not in the same location as your raid set).
In short, you need to back up your data even if you are using RAID. It is a serious error to think that raid provides data integrity.
In my view it would be better to simply not use raid but copy your data daily to different media since data integrity is probably more useful for most people, but of course not all. This is what I do on a regular basis. I have one disk holding my photos and two other disks containing backups of that same data (I am paranoid). If my main disk fails, I am guaranteed of not losing any data and I perform incremental and full backups using these two disks.