When I was evaluating personal finance software alternatives to Microsoft Money, my ex-money management software, high on my list of "must haves" was efficient and effective data files and backup. I've lost data before, and it hurts.

It was one of the things that drove me away from Microsoft Money. Its annoying habit of creating enormous data files (my last one is almost 40MB!) and not doing much if anything to protect them cost me too many lost afternoons recreating corrupted data files. If I were to adopt GnuCash to manage my money it was going to have to produce light weight data files and implement some kind of backup strategy to keep them secure.

I'm happy to report that GnuCash passes this test with flying colors. My most recent data file is just over 140kB. Yes, that 140 kilobytes. I've been using GnuCash for about 6 months now. Doing a little math... In about 3 years my data might take up a single MB of space on my hard drive. So much for lightweight data. What about backups?

Check out the General tab in GnuCash's preferences dialog:

I'm currently keeping 30 days' worth of previous versions of my GnuCash data files. In all that's about 7.7MB of space on my hard drive. Thirty days? Do I really need that many backups? Not by a long shot, but why not? They're so small it doesn't really matter.

For real backing up
Your master data file is the only data file you need to make a backup copy of when you do a "for real" backup - the one you copy to an external backup device. All of your data backup files - the ones GnuCash makes for you automatically - will have the same base name as your master data file, but with a time stamp appended to the file name. GnuCash creates and saves these every time you do a File | Save.

Backing up your data in GnuCash is simple. The files are small enough that you can keep hundreds of previous versions around. Why you'd need hundreds of versions I can't say. But knowing they're there just in case gives me a sense of security I could never get from looking at my single 40MB copy of my Microsoft Money data file.