On Tue, 2010-12-14 at 14:22 +0100, Rik Theys wrote: > 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? I don't think so. > 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? It wouldn't. I was thinking of Linux software RAID. Ben. -- Ben Hutchings Once a job is fouled up, anything done to improve it makes it worse.
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