On Tue, 14 Dec 2010, Ben Hutchings wrote:
On Tue, 2010-12-14 at 13:24 +0100, Rik Theys wrote:
This system _has_
a RAID controller and the disk is in a RAID1. Why would the filesystem switch
to read-only mode? Is it because the RAID is too slow? If the RAID is too slow,
this should just give a high iowait, but not make the file system read-only?
The DMA mapping failure will be treated as an I/O error. Most
filesystems do not attempt to retry after an error. This has nothing to
do with the speed of the disk.
Since you use RAID, the failure may only put a single disk in degraded
state, which will then be recoverable in the usual way. The error would
be hidden from the filesystem.
The RAID in this system is a PERC H200, which should be a hardware RAID card.
Can the mpt2sas driver see the physical disks that are part of the RAID?
It is my understanding that the mpt2sas driver only sees the RAID as a scsi disk
and not the individual drives? If that is the case, how would this I/O error
lead to a single disk in the RAID becoming faulty and the RAID degraded?
Will the H200 mark the disk as faulty when the mpt2sas driver triggers this?
Regards,
Rik
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