On Sun, 1 Jun 2014 19:23:39 +0200 Sebastian Herbszt <herbszt@xxxxxx> wrote: > NeilBrown wrote: > > > > On Mon, 26 May 2014 20:07:11 +0200 Sebastian Herbszt <herbszt@xxxxxx> wrote: > > > > [snip] > > > > How can I identify a failed array? > > > array_state reports "clean", the last raid member stays "in_sync" and > > > the value in degraded doesn't equal raid_disks. > > > > You know the array is "failed" when you get an IO error. > > > > When a RAID1 array gets down to just one drive remaining, it starts acting > > like it is just one drive. > > How do you tell if is single plain ordinary drive is failed? You get an IO > > error. ditto with RAID1. > > > > NeilBrown > > > > Since md knows the current state I hoped it would provide the required > information for an application to distinguish between degraded and failed > arrays. Any reason this is not the case? > This would allow mdadm to not only report "DegradedArray" but also > "FailedArray". Currently it does not generate any event when the last drive > fails. > But md *doesn't* know the current state. There is no state for "this device has failed". There is only 'an IO request has failed' or 'this device has been removed'. 'an IO request has failed' does not necessarily mean that the device has failed - sometimes that is a very important difference. NeilBrown
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