partman-auto-raid shown in docs but not on server cd (8.04)

[Joe McDonagh]

Hi All, this is a somewhat old (2 month) problem that has recently come 
back on my radar. I cannot for the life of me get partman-auto-raid to 
work in my preseed. The udeb doesn't even look like it's in the regular 
server distribution. I've tried anna-install/early_command, which does 
say queueing partman-auto-raid for install, but then it won't partition, 
so obviously that's not all I need to do. The documentation for 8.04 
seems to indicate there is no magic involved. Is there some special 
trick to this that I am missing?