A while back, I ranted about wanting servers designed from the ground up to function without a disk subsystem, which drew comments from quite a few folks who didn't seem to completely understand the main point. My bad -- I'll try to make it clearer today.
When I think of diskless servers, I'm not thinking about small businesses. I'm thinking of medium-size to large businesses virtualizing their infrastructures like mad right now. I'm thinking of data centers bumping up against power and cooling constraints. I'm thinking of a soon-to-be reality where local disk is useless. But it needs to go further.
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HP and IBM both now offer what they term a "virtualization blade." Neither blade has a traditional disk subsystem, opting for either flash or SSD-based boot devices and local storage. These may seem to be examples of what I'm talking about, but they aren't quite there yet. The required blade enclosure was designed for the maximum load of fully disk-equipped blades, not for these lower-power, diskless blades.
So imagine a blade chassis designed from the ground up to house completely diskless blades. Not only that, but these blades would be designed without a framebuffer: no disk, no video, just 10G Ethernet and Fibre Channel ports, two low-voltage multicore CPUs, and as many DIMM slots as possible. The power and cooling requirements for such a chassis would be different than those for a traditional chassis, as would possible blade densities. You'd get an awful lot of bang for your power and cooling buck.
Blades aside, I bet you could shoehorn at least three independent systems of this type into a 1U rack space. Lacking the disk subsystem, framebuffer, and associated parts and ports, you'd have only three or five ports on the back of each server (two 10G, one serial, or two 10G, two FC, one serial), and plenty of room for RAM.