On Sat, Apr 18, 2009 at 6:19 AM, Gordon McLellan <gordonthree at gmail.com> wrote: <snip> > I'm experiencing lots of kernel errors when reading or writing to a > disk that is part of an mdadm softraid-5 array. Since originally > detecting this problem, I have isolated it to one disk, but I'm not > sure what the cause of the error is. I have torn down the array and > have been testing the actual device now. > > I tested the drive several times using smartctl and the tests came > back OK / PASSED each time, and no kernel errors were logged. <snip> > Apr 18 01:10:00 xenmaster kernel: BUG: warning at > drivers/ata/libata-core.c:4923/ata_qc_issue() (Tainted: G ) <snip> What do those BUG warnings mean? (Tainted: G) Those appear various times, in the messages you posted. That driver has a problem?