So I upgraded Ubuntu 9.10 to Ubuntu 11.10 by _replacing_ my installation, rather than upgrading. Bad idea. When the system boots it says it cannot mount /store, my 960GB RAID+LVM file-system. That the one that holds over 10 years of personal photographs and such. :(

There are many layers of indirection between the file-system and the physical storage when using LVM or RAID. When using both, the number of layers can seem excessive. Here's a diagram of the layers involved in my (lost) setup:

Note that the RAID block device, md0, is not partitioned. I believe that was a mistake on my part, and a likely reason why Ubuntu 11.10 cannot auto-detect it.