$ rpm -q --whatprovides `which mdadm` mdadm-3.0.3-2.fc12.x86_64 If a raid drive (/dev/sdX) goes away (for example: because it was disconnected), then hotplug will remove the /dev/sdX{,y} entries. At this point "mdadm -f /dev/mdZ /dev/sdXy" and "mdadm -r /dev/mdZ /dev/sdXy" will no longer work. However: echo faulty > /sys/block/mdZ/md/dev-sdXy/state echo remove > /sys/block/mdZ/md/dev-sdXy/state works just fine. mdadm should probably be fixed...?
Hi, you should check the keyword "detached" for "-f" and "-r". According to the man page, "mdadm -f/-r /dev/mdZ /dev/sdXy detached" should fail/remove devices not anymore present. Hope this helps, bye, pg
Unfortunately, I don't believe that this is quite enough. The following is untested, but (and I believe this is actually the setup I had when I ran into this): - the array in question contained a read-only file system, as such no writes where ever issued to it - the device which failed was marked as 'write-mostly', so reads would never go to it, unless there were no non-write-mostly devices. As such the kernel would never attempt to access the missing device (writes impossible because of read-only filesystem, reads directed to other devices because of write-mostly) and thus would never mark the device as faulty. Hence the need to manually mark it as failed/faulty (and only then remove it). Furthermore I'm not convinced even the keyword "detached" would help us since the open doesn't return ENXIO - it just fails (the /dev/sdXy node is totally absent from the /dev directory because of hotplug). *HOWEVER* next time I run into this I'll try it and see if "-f detached" and "-r detached" or "-r failed" will work... I'll mark the bug as closed, and reopen if when I once more run into this I fail with the above-mentioned method.
The usage of mdadm -f detached or failed should work as it finds the devices which are part of the array and otherwise not operational and removes them. However, in future mdadm versions, mdadm -If also works and is going to be added to mdadm udev rules to cause devices that are hot-unplugged to automatically be removed from the raid array just as the device nodes are removed from /dev.
Awesome.