What is the common problems using an external hard drive to back up files?

1) A copy isn't a backup system. It is just a copy that puts all your eggs in one basket. 2) If you are copying files to the same place each time and the copy fails, then you have no backup at all. All you have is some of the old and some of the new and the corrupted bit; except when the external hard disk fades and you have nothing. 3) A good backup system gives you multiple copies. So, if you suddenly find that one of those important files that you have just copied to the external hard disk has really been corrupted or overwritten some time ago, then you've lost it forever. with a backup system, you can go back and recover that files from before it was lost/overwritteb/corrupted. Yes, tape is the best, but it is slow and/or very expensive for home use. Unless you buy 100year quality archival tape, a modern CD is just as good as the average tape, plus it gives faster acess for recovery. DVD will soon be as good. Break your data into lots of data 8.4Gb(?) for a dual layer DVD burner. 4.2Gb for a single layer DVD burner 640-800Mb for a CD burner. I would burn really important documents onto quality CDs atm. There was a stage that some CD's were duds, but they have been around for a while, you can trust the technology better than DVDs. It would be highly unlikely that you have more then 640mb of personal documents, business records, health records, etc. Every month, just burn a CD, or 2, or 3 with the latest and all documents. Label with a marker pen and slip into a plastic sleeved and into one of those bulk CD/DVD storers. "It would be a good idea to stash a set with parents, mate, etc just incase your house burns down. For your bulk files, like downloads MP3s, movies, games, etc, etc, sure burn that data off to single or dual layer DVD's. This is where backup software comes in handy. In business, you would take a full/complete backup once a week and then do a backup each day of the changed files. It probably isn't that important in a home system to be as rigourous. just backup a section whenever you add to it. Say you sort your music by the type and year it came out. Burn it all initially to a collection of DVD & Cds, then every time you add another song to a year, burn a DVD/Cd of that direction. Yes, this give you multiple copies on DVD/CD from which to recover stuff. Each year, you might do the whole lot again. Hint, do not put them into those expensive jewel cases.Get plastic sleeves and store them in those bulk DVD/CD filing cabinet that are around. Saves so much space. You will have a system that is just as good as those expensive tape systems they use in business.