I received a message:
kernel:[123456.789012] journal commit I/O error
Which disk drive had the journal error?
Search dmesg output for the timestamp value:
10 is the number of lines to show after the match. Increase if needed. It should start with something like:
You can identify that it's the same event because the timestamp is very close. In this case, it's a dm (device mapper) disk, but I think for normal drives it would show sda1 or similar.
To find out which drive this really is, do:
This only works if you use a label (if not, add one to all your drives for the future). If it weren't in the ext* family, you would have to use a different label command.