Hmm... I can boot 2.6.20-8-generic if I use a serial console, leading me to believe there's a race condition band-aided by the slower boot, but I do see mdadm segfaulting at one point in the log while booting 2.6.20-8-generic, which gives me some concern:
.... [ 78.098301] SCSI device sdd: write cache: enabled, read cache: enabled, doesn't support DPO or FUA [ 78.098302] sdd: sdd1 sdd2 < sdd5 sdd6 sdd7 sdd8 sdd9 > [ 78.739874] sd 3:0:0:0: Attached scsi generic sg3 type 0 [ 78.740198] sd 3:0:0:0: Attached scsi disk sdd [ 78.856399] sr 4:0:0:0: Attached scsi generic sg4 type 5 [ 79.008607] md: md0 stopped. [ 79.150105] mdadm[2930]: segfault at 0000000000000004 rip 000000000041567c rsp 00007fff3d930ab0 error 4 [ 79.271947] md: md0 stopped. [ 79.369580] md: bind<sdb1> [ 79.402051] md: bind<sdc1> [ 79.434502] md: bind<sdd1> [ 79.466950] md: bind<sda1> [ 79.502499] raid1: raid set md0 active with 4 out of 4 mirrors [ 79.572688] md: md1 stopped. [ 79.663216] md: bind<sdb6> [ 79.695665] md: bind<sdc6> [ 79.728121] md: bind<sdd6> [ 79.760567] md: bind<sda6> [ 79.795784] raid10: raid set md1 active with 4 out of 4 devices [ 79.866905] md: md2 stopped. [ 79.945377] md: bind<sdb7> ** Attachment added: "Serial console boot" http://librarian.launchpad.net/6487847/linux.log -- kernel/initramfs >2.6.20-6 fails to init RAID/LVM root https://launchpad.net/bugs/86384 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
