Bug#777140: Using mdadm to install Debian on Intel RST RAID array stopped working between Wheezy 7.8 and Jessie RC1

[anomie at users.sourceforge.net]

I ran into this problem recently on an ASUS UX301L. Worse, I ran into it
after *upgrading* to Jessie, the system wouldn't even boot anymore
because it couldn't assemble the root device.

After narrowing it down to mdadm and IMSM, I came across this
workaround:
https://bbs.archlinux.org/viewtopic.php?pid=1565988#p1565988

Executing "IMSM_NO_PLATFORM=1 mdadm --assemble --scan" at the initrd
shell finally allowed me to successfully boot.