they have a video demonstrating how to do server maintenance:

http://www.youtube.com/watch?v=EZmm7P1mPZs

no need to shut down the server. you pull it out and swap the parts (for front-accessible hotswap HDDs you won't even have to pull it out). cabling is designed to accommodate that.

i can imagine, though, that "pulling out" a 4U storage box fully loaded with hdds may become a bit strenuous.