On Wed, 18 Apr 2012 11:12:57 +0800 "." <desire@xxxxxxxxx> wrote: > Apart from the behaviour of the SCSI layer, does the linux software > raid layer have any concept of timeouts that would cause a drive to be > kicked when performing a deep recovery cycle? A storagereview forum > thread [3] claims that the linux software raid layer does not have a > concept of timeouts and does not care about ERC. In a web article [4] > the major NAS manufacturers that use software raid seem to agree with > this stance. Linux software RAID does not have a concept of timeouts. > > On the other hand, how I interpret a previous post from Stefan [5] is > that the linux raid layer does have its own timeout mechanism that > will kick a non-responding drive. That aspect of that post is inaccurate. > > > Without ERC-timeout, the drive tries to correct the error on > > its own (not reacting on any requests), mdraid assumes an error after a > > while and tries to rewrite the "missing" sector (assembled from the > > other disks). But the drive will still not react to the write request > > as it is still doing its internal recovery procedure. Now mdraid > > assumes the disk to be bad and kicks it. > > Since I can't read code, I'm hoping that this list where software raid > development takes place would be able to clear up whether > > a. Do delays caused by deep recovery cycles actually have any direct > impact on the linux software raid layer, or does it simply issue a > command to the underlying storage/scsi subsystem and block until there > is a response? md/raid in linux simply issues a command and waits for it to complete, either with success or failure. NeilBrown
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