ATA errors on one disk, failed other disk

vandermerwe wrote:

The backup issue could have many causes. I would start by looking at the backup configuration to make sure that's right, testing the USB disk, and looking at what's being baked up. You say no data on some days and the job still takes so long. Look at the backup job logs. The difference in time between your full and incremental jobs is not large, suggesting that the incremental jobs are backing up a large amount of data. What backup protocol are you using ?

An update, in case anyone searches in future and finds this:

I have just installed a new hard drive in my PC. I now still do a backup job from the NAS to the USB drive but also do another one to the new PC drive over the network.

The backup to PC is finished in under 10 minutes. It would appear to be a piss poor USB implementation on the NAS that is the trouble (this is replicated on two NAS and on four USB drives [EXT3 formatted] from different manufacturers).

The RAID array in question successfully completed the rebuild twice, with two replacement 2GB disks done separately and sequentially. It took about 12h for each rebuild.