I bought a USB 2.0 hard disk enclosure (for both PATA & SATA 3.5" ) and put my WD1600JB 160G ATA hard disk in for backup. I copied a couple of 1GB files onto it (no errors reported). Later, I compare the files with the origins and they were different. Then, I ran md5sum checking on those files and it failed about once in three/four times. It seems that the transfer of large files from the external drive (maybe both direction) was unreliable.

The whole thing was tested on 3 different computers and USB cables but no luck. But the hard disk was okay with direct IDE connection. What should I check further? Should I get another USB enclosure? It's weird that no errors were reported by Windows. Is it supposed error checking/correction mechanisms are built in the I/O (USB and IDE)?

Any idea? Thanks a lot!

Switch to Linux instead?

Thanks for your advice. Tried Linux and got similar results though it seems a bit better in md5sum test. it failed once in 7-8 times.

It could be faulty, or maybe doesn't support drives bigger than 137Gig (unlikley), my guess it's probably just a pile of ....

I had pretty much the same symptoms with a direct IDE/SATA to USB adapter (the ones without the enclosure, connecting directly, cost 15$).

After several mismatch and errors while trying to read the copied files, I decide to not use it anymore in my backup process. I have no idea what goes wrong in the process though.

I format the partition as ext2 on Linux and did the md5sum checking again with an additional large file. It's found to be much more 'reliable'. But there was still one failed check.

I think this should be an alert to using external hard disk for serious backup especially with those cheap stuff.

We do have a lot of different enclosures or external hard drives perfectly working here though.

Maybe you got a bad apple? What brand / model is the enclosure?

It is not any well-known brand name. Just a basic aluminium enclosure with an electronic board and a metal plate inside.

How many people test back-ups?
How would you know if one back-up in 5 (or 10) had failed?

I back-up 200+gig of data on a weekly basis onto USB hard drives, so far (thank God(s)) I haven't had need to test the validitity of the backups...

MrLinux,
Basically doing any backup especially for system one should test the whole backup and recovery process. This makes sure every thing goes right for that purpose. Otherwise, you spend time on it every week and one day all luck is gone and you find that it doesn't work as expected.

I should have paid 50% more for a reliable storage media that would save me lots of time.