I have a Linux server that I use, running Redhat 9. It stores all my files and while it's been up now for a few months I still haven't really got a good automatic backup solution.

I happened to see some very cheap (i.e. around £15) RAID cards. I know that Linux can do software RAID, but I am under the impression that it's quite hard to setup. For such a cheap RAID card, I'm obviously not expecting brilliant transfer rates, but then I'm not really expecting much in that department from my file server. Most of the product reviews I have seen though have said good things about the products' functionality.

Can anyone give me any advice on this matter?
It took me a damn long time to get Linux exactly how I wanted it and now that it's in that state it functions perfectly... so I'd quite like to backup the entire parition and do frequent backups... So as far as I can see RAID 1 is perfect.

Most hardware RAID setups have a utility, more like a bios, where you create or manage the raid array. It will likely be the case in this instance, however you didn't post the card you are looking at so we can't say if its a good or badly supported card. I doubt it wouldn't be supported, but you never know. Also, your performance is going to drop with mirroring, not incredibly but some. RAID 1 (mirroring) simply creates 1 backup (mirror)drive in case the primary one fails. This is not a substitute for daily,weekly,monthly backups. It is meant for continued operation due to drive failure.

Tips
Create a scheduled backup plan, cause it doesn't sound like you have one.
Make at least 1 full backup before you do anything to that server.
Read up and do a search on "Redhat _____ raid card" inserting the card name/number
Make a second full backup, cause you can never have too many when you screwing with production servers.

Post the card so we can shoot down your idea, or tell you to go for it.