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I've been reading about backup solutions and have come across a number of people saying they use a USB external hard drive as part or all of their backup solution.

Are USB hard drives really sufficiently reliable to use for backups? From what I read in the past (e.g., http://blogs.computerworld.com/why_im_done_with_portable_hard_drives) they are rather failure-prone, especially apparently USB-only ones where the USB controller electronics have a high failure rate. Personally, I've only ever had one, a mid-price Western Digital, which has had some issues and I stopped using.

I understand there are some factors that substantially affect reliability, which AFAIK are whether the drive is moved much, whether it has its own power supply, and whether it has adequate cooling. Perhaps the drives are more reliable now than they used to be? Perhaps if they last through an break-in initial period they then tend to be reliable?

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4 Answers

up vote 7 down vote accepted

"...part or all of their backup solution."

USB HDDs for part of the solution is okay. For all of the solution, it's not a good idea.

When you plug in your USB HDD, your entire backup medium is now online and writable, on the same machine which has your primary data.

In the event of:

  • a glitch in your backup software
  • an electrical failure
  • a virus
  • human error
  • fire or flood

You could lose all your data, even your backups.

One poor-man's solution would be to use two HDDs, keeping one off-site and off line (e.g., at a friend's house).

The disks are reliable. Some USB electronics are flaky, so test your backups.

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Great answer. I'd add that using an external USB enclosure which can be disassembled easily and hard disk removed, allows you to recover data in case USB enclosure electronics fail, but the hard disk inside is ok. – haimg Dec 13 '11 at 18:34
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+1 Also, backing up to a USB is going to be slow, especially over USB 2.0. eSATA may be a better choice for external drives. – Amazed Dec 13 '11 at 18:39
+1 for test your backups. – afrazier Dec 13 '11 at 21:01
I was hoping for real data on the reliability of USB drives, but I suppose that isn't the precise question I asked, plus I'm starting to wonder whether such data really exists. Still, if someone has that, I'd be happy to give them credit instead of I can. – Paul Dec 14 '11 at 19:06
There is a huge array of USB drives, so answering that question in general is very hard. You can look up reliability for most individual drives, especially the upper end ones, on the manufactures websites. Also, it will matter to a degree how much you move/toss it around. As a general rule, they are reliable enough that its not an issue for an average end user, but no existing medium is so reliable as to be trusted for a sole backup. – TimothyAWiseman Dec 14 '11 at 22:41
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up vote 1 down vote

I agree with mgjk but to expand on it a little, USB harddrives are relatively reliable. I have had some last for several years. I have had some fail on me, but then that is true of the primary harddrive inside the computer too.

Any harddrive, indeed any storage medium at all, will have a failure rate. That is why for files that are truly valuable you should have redundant backups, no one solution will be perfectly reliable.

At home I backup my files automatically to my NAS as well as using dropbox for many of my key files (in conjunction with truecrypt for the sensitive ones.) I also occassionally burn a DVD with the files that I know I want to archive for the long term. I would not fully trust any single one of those solutions, but together I know the odds of them all failing at once are acceptably low.

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Thanks, your data is very helpful. I've actually been very fortunate with internal drives, perhaps because I tend to replace them after a couple of years. – Paul Dec 14 '11 at 19:09
Yeah, I tend to keep upgradin computers rather than replacing wholesale, so I have harddrives die on me from time to time. – TimothyAWiseman Dec 14 '11 at 22:37
up vote 1 down vote

The point of backing up is not to not have failures. Its to not have a failure when you have another failure going on at the same time, and the thing that failed is needed to fix something else thats failed.

Nothing is failure proof, you're playing with failure curves. Internal drives fail, external drives fail, every so often entire BUILDINGS AND INFRASTRUCTURES fail.

So, yes they are. Just don't entirely trust the sneaky buggers and have enough backup backups to sleep well at night ;p

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up vote 0 down vote

I've had 2 USB HDD's fail on me in the past. Both due to HDD failure (the USB enclosure is still working; verified by plugging the HDD into another computer).

100% of my failures have been due to accidently dropping the drive, having it fall off a table, having the cable wrenched out at unexpected times, etc. Basically, my own negligence and stupidity.

I fixed this problem by taking the HDD out of the USB enclosure and connecting it via the internal SATA interface in my home media PC. There have been zero failures over an equal period of time since I took me out of the equation!

Remote backups are done via a remote backup service over the Internet.

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