Why RAID alone is not the answer for backups

I recently came across Gina Trapani’s article on the importance of backing up (the comments are worth a read too). I hear what she’s saying – a couple of years ago I very nearly lost a lot of data when a hard disk died and today I have far more important stuff on disk (like all of my recent photography – including irreplaceable pictures of my son – a digitised music collection and years’ worth of accumulated information), all spread across nearly a terabyte of separate devices.

As we place more and more emphasis on our digital lifestyle, the amount of data stored will continue to grow and that creates a problem, especially for home and small business users.

Optical media degrades over time and since the hard disk I bought for backups is now in daily use with my new Macintosh computer, I need to implement a decent backup regime. As disk sizes increase, a single disk seems like putting all my eggs in one basket, but I also hear people talking about how RAID is the answer.

No it’s not.

The most common RAID levels in use are 0 (striping), 1 (mirroring) and 5 (striped set with parity). RAID 0 does not provide any fault tolerance, RAID 5 needs at least 3 disks – too much for most home and home office setups – that leaves just RAID 1. Mirrors sometimes fail and when they do, they can take all of the data with them. Then there’s the additional issue of accidental damage (fire, flood, etc.). What’s really required (in a home scenario), is two or more removable hard disks, combined with use of a utility such as rsync (Unix) or SyncToy (Windows) to automate frequent backups, with one of the disks kept off site (e.g. with a family member) and frequent disk rotation.

In an enterprise environment I wouldn’t consider implementing a server without some form of RAID (and other redundant technologies) installed; however I’d also have a comprehensive backup strategy. For homes and small businesses RAID is not the answer – what’s really required is a means of easily ensuring that data is secured so that if a disaster should occur, then those precious files will not be lost forever.

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