[dm-devel] Buffer I/O error

[Kit Westneat]

Hi dm-devel,

I'm running into an issue with dm-multipath 
(device-mapper-multipath-0.4.5-27.el4_6.3) that has me confused and I 
was hoping I could get some guidance.

Here are the relevant dmesg messages:
device-mapper: dm-multipath: Failing path 8:48.
device-mapper: dm-multipath: Failing path 8:48.
device-mapper: dm-multipath: Failing path 8:48.
device-mapper: dm-multipath: Failing path 65:80.
printk: 1004 messages suppressed.
Buffer I/O error on device dm-13, logical block 1192525829
lost page write due to I/O error on dm-13

Normally when I have seen Buffer I/O errors in the past, they have been 
accompanied by SCSI errors as well, but in this case I am not getting 
anything. One odd thing is that the filesystem reported extremely slow 
writes before the buffer I/O errors occurred. I have checked and 
double-checked the storage array and everything seems fine. I am using 
directio as my path checker if that makes a difference.

I have been able to reproduce the problem consistently by attempting an 
fsck on dm-13. However, I am now doing an fsck on the underlying sd 
device and it hasn't bombed out yet with the buffer I/O errors.

Has anyone encountered these seemingly inexplicable buffer I/O errors 
before? Any advice on how to debug it?

Thanks,
Kit Westneat