I just set up a RAID-5 composed of 3 new Western Digital USB hard drives, each 1TB large. The three drives are connected to the system through a USB hub. The total size of the array is 2TB, formatted as ext3 (largefile4).
I know this USB raid is slow (about 15MB/s slow...), but we ran out of space, SATA ports, and USB ports in the system unit. That's what we get for having to run a server on a budget. We are planning to use the array for semi-long-term storage of large files (DV-AVI files), and decided that sacrificing speed for the redundancy was alright.
Anyway, I moved a large file into the array. Later, while reading the file, I got a read error halfway into the file. I thought it might have been a freak incident as the array was still being resynced when I formatted and copied files in. Also, /proc/mdstat said that all three drives are fine, so I reformatted it again.
I had just started to copy files into the newly formatted array when two of this kind of message pops up on my tty:
EXT3-fs error (device md0): ext3_new_block: Allocating block in system zone - blocks from 131334144, length 1
I'm starting to suspect the "freak incident" was not a random incident... Does anyone know if anything else could be causing this? (besides hardware failure?)