(original article)

Re: A Nasty md/raid bug

12 August 2012, 22:34 UTC

If you ask a question on the blog, you get a reply on the blog. If you ask a question on linux-raid you get a reply on linux-raid....

The array isn't starting at boot time because it is degraded. This suggests a problem with the boot scripts. I suspect your distro ('arch'?) is relying on "mdadm -I" being run from udev to start the arrays. This by itself isn't always enough. After all devices have been discovered you need "mdadm -Irs" or "mdadm --incremental --run --scan" to assemble any newly-degraded arrays.

So in some script before it tries to mount filesystems you want something like:

udevadm settle mdadm --incremental --run --scan

This will have to go in a script in the initrd of course.