With the low power ARM processors becoming very popular because of smartphones and tablets, Canonical is trying to expand the architectures which Ubuntu supports by including ARM as well. Technically, Ubuntu can be run on ARM machines as well but the Canonical servers does not build ARM packages. So, anyone who wants to use Ubuntu on ARM have to manually build them.
With Ubuntu planning to officially support ARM, they need to build packages for the ARM architecture as well. The job of building an Ubuntu ARM build machine was given to David Mandalla.
The ARM cluster server that Mandalla is building makes use of the relatively cheap PandaBoard. Each PandaBoard software development platform has a dual-core ARM Cortex A9 processors running at 1GHz and a low power 1 GB DDR2 RAM.
The ARM build machine that Mandalla is developing has 21 PandaBoards with each board connected to a 300GB hard drive. This brings final specifications of the machine to 42-core ARM processor, 42 GB DDR2 RAM and 6.3 TB of storage.
Out of the 21 boards, 20 will be used to build Ubuntu packages. One board will be used as the master board to allocate the build requests received from users to the other 20 boards.
Mandalla is documenting the build on his blog. You can read more at his blog.