Anyway, I hear about people re-backing up their data yearly.
Is having all my data backed up on one HDD a bad idea? I been using it for maybe about 2 years now. Right now I have about 1.5 TB of back up data. If I want to back up my back up, does that mean I have to have have another HDD that holds 1.5 TB of data, or is their some special way to do this dealing with image files and all of that?
Say if that HDD all the sudden messes up, and no data shows up when I am using it, is there a way to restore all that data?
The general rule is to make backups in proportion to how important your data is to you. The other rule is to make lots of frequent backups.
If you have important data, you should have more than one backup. You should even consider having one or more of your backups stored in a different house or building. Having only one backup is a bad idea. If your drive "messes up", there may be no way to restore your data. 2TB external drives can be found for relatively low prices, I think a couple of these could supplement your backups.
If the data hasn't changed, then there's no particular need for you to back it up again. But hard drives can and do fail - so if you're not actively using your hard drive to do more backups on a regular basis, then it may stop working without you knowing about it.
It's just as likely, or probably even more likely that it may stop working even if you use it regularly - the difference is that you'll find out about it when it does and you can do something about it before it becomes a problem. The last thing you want is to have your main system fail and then discover that your backup drive doesn't work either.
There are two ways to reduce the chances for this to happen, and for the best protection you'd use both of them:
1) Keep two backups of your data on two separate hard drives. Ideally, you'd store the two drives in different locations, one of them offsite. This way, you need to have three drive failures (main system and both backups) before you're hooped. Three failures is a lot less likely than two.
2) Check your backup drives regularly (perhaps every month?) to make sure they're still working. The best way to do this is to use a checksumming utility to create a list of checksums for all of the files on the disk. Then, on a regular basis, use the utility to read all the files and confirm that their checksums haven't changed. This way you know for sure that (a) the drive works, and (b) every bit on the drive is readable and hasn't changed surreptitiously.