Rule 1: Every mechanical device fails.A fairly new technology getting more widely deployed is Solid State Disks, storage that is made from memory chips rather than rotating disks. This helps a bit with Rule #2, but only a bit. Sure, there's no drive, platter, and spindle anymore, but if your house burns down you have lost the SSD just like you would have lost your traditional hard disk.
Rule 2: Every hard drive is a mechanical device.
Rule 3: It's the data you care about.
Redundancy. Don't back up once because two is one and one is none.
Two is one and one is none.
So think about your data, and how many copies you have:
1. You have a copy on your computer. This is one copy, but remember: one is none.
2. You have one on your backup device, once you've backed it up. That's two copies, but two is one and one is none, amirite?
3. You need something here. Long time reader, friend, and biker dude Burt emails about this:
Be very careful with single-disk backup solutions. If the single drive dies, you're screwed.
RAID stands for Redundant Arrays of Inexpensive Disks, and has been around for years and years. You won't get one of these for $115 at the Big Blue Box store, but you can get twin disk RAID devices for maybe $300. Each drive mirrors the other automatically (RAID-1). The downside is that you only get half the storage space; the upside is that you get item #3 above, which gives you your third backup location.If you're gonna use a locally-connected backup system, at least use a RAID-1 (mirrored) system. That way, if one of the drives fails, you can recover your data and transfer it to another media before the other drive fails. (I use 2 NAS systems: one is a 2-drive RAID-1 system, the other is a 4-drive "striped RAID-5" system - and some data resides on both systems.)
If you get a twin disk RAID-1 backup drive, you will have three copies: on your computer, on the first disk of the backup drive, and on the second disk of the backup drive. At this point, a lot of stuff has to go bad for you to lose your data. That can happen, but now you're talking about catastrophe, like your house burning down. I'll deal with that tomorrow in Part III (off-site and cloud backup).
Two is one, and one is none. You want to aim for three. You also want software that will do this automatically for you. That will be Part IV.