Dell has more details on its XS23 Cloud Server. Seems like this is the kind of server's good for containers as well.

XS23 Cloud Server
Tue. May. 13, 2008
There has been some recent press around some of the equipment we’ve developed in our cloud computing group. The core of our business is essentially a consulting and design service and developing new products for customers is a big part of the fun. Because these aren’t mainstream PowerEdge systems, we don’t get the chance to show them off as much as we’d like. Our group has been talking for some time about “optimized designs” for cloud and hyperscale computing without showing what that can really mean, so it’s time to unveil something that’s come out of the lab. Pictured here is one of our favorites: the XS23.

XS23 front – twelve 3.5” SAS or SATA drives; 3 per server
This product was designed for a customer that needed maximum compute density, a healthy amount of local disk and, of course, lowest power draw possible. Our architecture team threw all that in the blender and out came a 2U standard rack mount chassis that houses four dual-socket servers and twelve 3.5” hot plug drives.

The energy efficiency design is driven by customer requirements. Yippeee!!! Cloud Computing and HPC customers are driving the requirements for Greener HW designs.

This was expressly designed for an environment with high node failure tolerance - a cloud application. By designing out a lot of the capabilities that weren’t required (like redundant power) we were able to deliver the performance and power profile required. Efficiencies are gained by shared resources - as seen in a lot of general purpose designs available today. We think the key to designing the perfect cloud server is knowing where to stop and also what not to build in. This is a function of each customer’s unique design goals.