Hello, thanks for the quick and helpful responses! Answers inline: > Step one is confirm that it is easy to reproduce. > Does > dd if=/dev/md0 bs=4K skip=1598030208 count=1 of=/dev/null > > trigger the message reliably? > To check that "4K" is the correct blocksize, run > blockdev --getbsz /dev/md0 > > use whatever number if gives as 'bs='. blockdev does indeed report a blocksize of 4096, and the dd line does reliably trigger dd: error reading '/dev/md0': Input/output error and the same line in dmesg as before. > Once you can reproduce with minimal IO, do > echo file:raid5.c +p > /sys/kernel/debug/dynamic_debug/control >repeat experiment > >echo file:raid5.c -p > /sys/kernel/debug/dynamic_debug/control > > and report the messages that appear in 'dmesg'. I had to replace the colon with a space in those two lines (otherwise I would get "bash: echo: write error: Invalid argument"), but after that, this is what I got in dmesg: https://paste.ubuntu.com/26305369/ > Also report "mdadm -E" of each member device, and kernel version (though > I see that is in the serverfault report : 4.9.30-2+deb9u5). mdadm -E says: https://paste.ubuntu.com/26305379/ The kernel has been updated between the serverfault post and my first mail to this list to 4.9.65-3+deb9u1. No changes since. > > Then run > blktrace /dev/md0 /dev/sd[acdef] > in one window while reproducing the error again in another window. > Then interrupt the blktrace. This will produce several blocktrace* > files. create a tar.gz of these and put them somewhere that I can get > them - hopefully they won't be too big. I had to adjust the last blktrace argument to /dev/sd[b-f] since after the last reboot the names of the drives have changed, but here's the output: https://filebin.ca/3mnjUz1OIXqm/blktrace-out.tar.gz I also included the blktrace terminal output in there. Thank you so much for the effort! Please let me know if you need anything. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
