As our own Emil Protalinski noted in his column yesterday, Facebook is very happy with the results of their year old Open Compute Project (OCP). Despite being the new kid on the block when it comes to building datacenters (they only have the one, so far), the OCP has seen quite a lot of vendors jump on board the design standards that Facebook has been responsible for setting.
But the most lasting impact of the project may well be the Open Rack Standard. With the open rack standard you get what are basically server racks stuffed full of blades, with separate power trays that support servers, networking and storage in the same rack design. While you are probably just thinking no big deal, it's a giant blade server, you would only be partially correct. The design spec for the Open Rack calls for a 21" rack, not the ubiquitous 19 inch rack found in just about every data center currently in existence.
This 2" change in the standard is a huge one. There are lots of good reasons for it, ranging from it allowing the installation of five 3.5" drives across the blade, rather than 4, to the additional space for CPUs and memory (remember that power is provided external to the boards). And Facebook is not the first organization to propose this change: there is a Project Scorpio standard being proposed by three huge Chinese web service providers, as well (discussions are in place to bring about a convergence of the two proposed standards by 2013). And IBM has had 24" racks for quite a while, which are used in their mainframe and mainframe equivalent server deployments.
Issues of what can be done with 21" racks rather than 19" aside, the change would be a huge one on the infrastructure of current datacenter and datacenter designs. Those facilities are designed around the 19" rack. While 2" doesn't seem like a major architectural change, everything in most datacenters is laid out based on that 19" rack spacing. Cable runs, power, raised floor tiling, ad infinitum. The switch to 21": racks will impact all of that. And for datacenters users with modular or containerized systems, the impact would be even more significant, as many of those designs are configured around maximizing density, power, and cooling based on 19" rack spacing.
Facebook may be responsible for some current social upheaval, but who thought that their most lasting legacy could be 2" of rack space?
Update: I was contacted by a representative of Facebook who wanted to let me know that even with the change a 21" rack mount, that the external dimensions of their standard rack would remain the same 24" spacing currently in use.