We recently got Dell R900 box to use as a benchmarks so in addition to looking remotely to a lot of them we could pick an eye inside.
Inside it is nicely designed box with everything pluggable. It has 32 memory slots making it possible to get 128GB of memory with less expensive 4GB DIMMs. It takes 4 quad core CPUs and comes by default with 4 network interfaces…. It really looks like it is designed to be virtualized as 4 boxes in one. Indeed you can get 4 virtual slices with 4 cores each, dedicated network card and 32GB of memory. It also has plenty of PCI-E slots for extensibility.
What I did not like though (and this is my general concern with Dell/HP/IBM/Sun) – They have very low limit on number of external drives. This is 4U box which is twice as high as PowerEdge 2950 but it still only takes 8 2.5 inch drives. The rest of space is used just for the fan holes.
I do not believe this is done for cooling reasons, especially as SuperMicro manages to fit 24 of such hard drive slots just 2U chassis. I think it is just a silly trick to make people buy external storage if they need more drives, which is typically the product with higher premium.
Though it is a good question if we will need so many drives in the future. Most people getting many drives these days do it for performance reasons and SSD may eliminate this need… and even 8 SSDs should be offering enough space and performance for many needs in 1-2 years timeframe.