USB Flash Drives for Backup/Long-Term Storage?

cyberdigm is curious about this issue: "I am writing two books and have just recently gone through the trauma of having my hard drive flake out (physical damage to several sectors). Fortunately, while the OS instance was trashed, the file system is still intact, so I have been able to recover my files.Given that, I am now much more aware of the needed to regularly back up my files. I'd be interested in any opinions about the suitability of USB flash drives to help me solve this problem. The idea would be to store copies of all my files on a USB drive and back them up every day. I like that USB drives are generally fairly cheap. My concern is the long-term wisdom of this approach. Are there (practical) rewrite limits for USB flash drives? Is there a chance that the data would degrade on the drive over time? Other alternatives I am considering include external/USB hard drives. Of course, an overarching concern is that I'd rather not spend a lot of money."

Comments

Practical Concerns

[Marxist Hacker 42]

Experiences in using flash memory for backups on PocketPC:

#1: Rewrite limits. Currently, flash memory has about a 1 million rewrite limit theoretically. In practice, though, I had a CompactFlash card (no real different technology from the USB drives other than interface to system) fail after about a year of daily backups.

#2: Time-to-destruction- I once left pictures of my honeymoon for nearly 6 months in my digital camera, also using flash memory. After 6 months, the files had a 50% corruption rate. So I wouldn't consider this a very long term storage solution- at least not without refresh.

Asside from those concerns, it's a very cool idea- especially if you kept the backup software on the key and increased your potential by using say, 7 keys (one for each day of the week) and kept the backups off site.

Re:Practical Concerns

[name773]

there are two sides to a magneto optical disk: a floppy-like side and a cdrom-like side. a laser heats the cdrom-like side until it hits a temp. where the magnetic portion directly below that hot point can be changed. a magnetic head then changes the polarity of that hot spot on the magnetic side. the disk is read from the optical side, and the dot on the optical side reads differently depending on the polarity of the dot directly oposite it on the magnetic side of the disk. this gives you over 1e6 rewrites, and the disk won't demagnetize under a certain (high) temperature. also, the shelf life is 50-100 years, in part due to the plastic (3.5" floppy like) casing mentioned by the parent. the disadvantage being that these drives are slow and expensive... slow because the drive checks what it just wrote and corrects the write if it's faulty (i think on a per dot basis). the upside is reliability.
magneto optical discs get anywhere from 128mb to 5.2gb that i've seen, and they come in three varieties: minidisc, which is primarily for audio, but a few data ones are being sold, the old version holds ~1/5 of a cd, so ~130mb, the newer version (uses multiple layers) holds 1gb, and i don't know if they have a data version or not. 3.5" mo discs come in 128mb-1.3gb that i've seen. slightly older drives accept 640mb discs while the new ones take 1.3gb discs. this value may have increased since i last looked for a mo drive. 5.25" mo discs come in sizes up to 5.2gb so far as i've seen; this value might be bigger now.

RAID 5

[xornor]

My computer has 6 usb ports, get 6 usb flash drives and RAID 5 them. If one dies replace it ;)