I confirm this problem in Archlinux 1.1.1 image: I can boot smoothly from SD card, mount my external HD (sda) and access the content of the second partition (sda2); where I also dd'ed the Archlinux image.|
If I change uEnv.txt root parameter to =/dev/sda2 and try to boot without touching the physical setup (same devices attached to the same cables, same power source, etc...) the booting sequence halts while waiting for root filesystem (/dev/sda2) forever (because of rootwait parameter). If I limit the wait to 30 seconds the boot sequence continues, but the system crashes before completing it because the lack of root.
If I unplug and re-plug the HD the console shows informational messages about the disconnection and re-connection, identifying the USB device as a Hard Disk (including vendor ID and other info), so the kernel is aware that there is a USB HD connected... so the problem could be in the initiation scripts and be related to /dev not being populated before trying to mount root, but that exceed my technical knowledge.
Hope this help someone more skilled to fix this.
Thanks in advance