I have a pet peeve and it is people who don't back their shit up. To quote Scott:
AprecheY U NO BACKUP?
In the spirit of not just telling you to back up, here is how to do it, and how to do it well.
1) Back up to the cloud. This costs about $50-$60 per year, choose any of the many providers. I use JungleDisk which is a nice front end to Amazon S3 and CrashPlan which has their own data centers. Amazon S3 is great because it is huge and reliable. Also, your storage is accessible via public API's and in an emergency you can write a three line python script to get it all back (JungleDIsk actually provides a free open source program for this on their site). Finally, Amazon S3 is cheap; for small amounts of data (hundreds of MB's) it is literally pennies a month. CrashPlan is free unless you use their own cloud storage. They have a neat inbuilt system where you can give space on your machine for a friend's backup or just backup all your machines to each other. I use their unlimited plan for $36/year (you have to buy a 4 year plan) which is for one computer plus attached drives.
2a) Local backup. If you have a desktop, permanently attach an external drive to it. If you have a laptop, attach the external disk to your WiFi router (if your router does not support this, get yourself a modern router).
2b) Use some software to do the backup for you. This will cost some amount of money, possibly 0 since there are some free programs out there (e.g. CrashPlan, Carbon Copy Cloner). If you need to do it yourself, you will
forget. I use ChronoSync (mac only) because it has customizations out the wazoo. I back up all my machines to a RAID disk that is attached to a server and that server backs itself, including the external disk, up to CrashPlan. This is in addition to each machine individually having an automated JungleDisk backup running.
You need to do both 1) and 2). If your house burns down and you lose all of your data, then it was not
a backup. If Amazon flubs big and your data is gone, then it was not
a backup. Don't call it a backup if it is not a backup.
A couple more general points
Never, ever, mirror your data. This, coupled with automatic backups can result in a glitch where your backup gets corrupted and backing up corrupts your data. Always have primary backups be one way only and keep copies of deleted/modified files. After that you can have a secondary backup which is, e.g., a cloned image of your boot drive.
Always have reporting. JungleDisk had an RSS feature that reports every backup, successful or not. ChronoSync has customizable emails, and I have my mail filters set up such that warnings get flagged. CrashPlan is the best, since their server end will actually email you if your backup hasn't happened within a specified timeframe.
A backup is never a backup if you can't get your files back. So after setting everything up, test the setup by retrieving some files. Note where you need to know passwords and try to figure out if you could do the retrieval without them (e.g. by requesting new ones). If there are passwords which are absolutely necessary, write them down on a piece of paper and store it safely somewhere else
than your house.
This last one is to protect your strategy from biological memory loss and, in case you are backing up not just your own data, from the possible bioligical loss of yourself. Write down your backup strategy with specific instructions on how to retrieve the backup. Give to a person you trust.
So, how do you back up? Feel free to suggest improvements to my setup.