eWeek is reporting a rumor that Facebook are about to begin the move away from leased colocation to building out their own datacenters. What we do already know is that late last year Facebook leased out 10,000sq feet of datacenter space at a new facility built by DuPont Fabros Technology in Ashburn, Viginia, alongside both Yahoo! and MySpace. The lease coincided with a $240M investment from Microsoft which was announced at around the same time as the datacenter lease was organized. More recently, they raised a further $100M in March of this year specifically for infrastructure spend.
With Facebook now at beyond 10,000 live web servers, they are certainly able to reap greater benefits and cost efficiencies through building out their own hosting centers and infrastructure. With over half-a-billion dollars in funding, it certainly seems that Facebook are well into building out their own datacenters and infrastructure, with what is likely commodity hardware components for servers and a custom application stack. Facebook have also owned their own very large IP address space for a long time now and have managed it themselves.
Facebook use well-known technology stack, with Linux, PHP and MySQL. They claim to run one of the largest MySQL instances on the planet, and have contributed a number of patches to various open source projects. Vendors looking to line up Facebook may face a bit of a challenge, as like Google, they seem to keep a lot in house and build on open source (there were event rumors recently that Google were now even building their own switches).