My company recently wasted a lot of time restoring data from corrupted USB disk backups. Everyone here is now keen to prevent the same happening again – but before buying the $5K tape drive now recommended I wanted to investigate a bit further.
The data recovery company that helped restore our data told our engineer that backing up to USB disk is a stupid idea. I wanted to find out why this might be, but have so far failed to find any likely reason. The only issues that I can think of that might affect these backups are
- Physical damage to the disks. Although disks are less robust than tapes, it seems unlikely as the disks themselves are readable and were not badly treated.
- Failing to eject the device before unplugging (also seems unlikely, as the disks would in any case typically be unplugged long after the backup finished)
Does anybody know of any fundamental problems either with backing up via USB, and/or to disk? Is NAS any better? My suspicion is that it was the fact that backups were never checked (no test restores ever done) that was the problem, not the fact that the backups were on disk or performed via USB.
For background… :
The fault we experienced: One day the server crashed due to a motherboard fault, resulting in corrupted data on a RAID disk pair. When it came to restoring the server, we found that the USB backup disks (which had apparently verified ok) were mostly unreadable. On the one BKF backup that I checked it seems that it became unreadable was the MS Exchange database folder. We managed to restore data using the rather clunky but usable 'systools BKF repair'.
Our precautions against data loss consisted of
- RAID disk pairs, with windows sever set to record 'previous versions' of files
- Weekly backup/verify of complete SBS 2003 server (~200GB) to 500GB USB disks
- Daily incremental internet backup of user data (~60GB)
Best Answer
What kind of RAID? Motherboard-based? (couldn't tell from the description)? That is a problem if it is.
As for using USB disks, I don't think it's a bad idea necessarily, as long as you are verifying the backups and the speed/capacity are adequate for your purposes.
Our current tape backup solution has a dedicated server (using Microsoft DPM) that saves backups to a local hard drive, then rotates out the backups after a period of time to tape for longer term storage.
USB can be slow, but again, if it's meeting your needs then there's nothing fundamentally wrong with it. The thing to do is sit down and analyze your options and disaster recovery plans. How far back are you able to recover data? Are you able to recover from bare-metal failure? How long of a downtime would it be? Are your backups taking too much time to perform or hindering server performance while users are trying to get work done?
Also, how available is the data? Tapes are high-capacity and easier to store for a period of time, but if you need data on a tape that your drive no longer reads or can't get new tapes for your device because it's too old, what then? Hard drive backup tends not to have this issue, as there are tapes that you can have trouble reading from ten years ago but USB will be around and usable for quite some time in all likelihood.
And is your solution proprietary? I.e., the old unix tarballs from way back when dragons were real and pirates didn't have law degrees can still be decompressed and read. If your backup is in a format specific to a product, do you think you can recover data if the program is no longer supported or has other issues?
What it boils down to is analyzing your situation and coming up with recovery scenarios and making sure you're covered in the most likely events. USB drives are fine, as long as they meet your needs. But they also can be prone to any other hardware failure, so you should probably make sure to cycle them out periodically for redundancy.