San Diego, Calif.-based Verari Systems has joined Sun Microsystems and Rackable Systems, Inc. in the data center mobilization trend with its new Verari FOREST containerized data center.

These mobile data center offerings address the need for space and low cost power. Companies without room for more servers can buy one of these containers for less than it would cost to build a brick and mortar data center, fill it with servers and storage, and plop it down in an area where electricity costs are low - like an abandoned coal mine in Japan.

Case in point, Verari’s FOREST container can house up to 1400 blade-based compute servers or nearly 12 petabytes of blade-based storage using Verari’s new BladeRack 2 X-Series platforms in the modular unit.

Sun’s containerized data center, project BlackBox, is in a standard metal shipping container — 20 feet long, eight feet wide and eight feet tall — and can house about 250 single unit rack servers. Introduced in March 2007, Rackable Systems Inc.’s Concentro is a 40 foot by 8 foot shipping container that houses up to 1,200 of Rackable Systems’ rack-mount DC powered servers and up to 3.5 petabytes of storage. The company came out with a denser mobile data center called ICE cube in October. IBM came out with one, the Scalable Modular Data Center in July 2007.

Who first invented the idea of a mobile data center? Probably Google, which patented the containerized data center in October, and which reportedly has been using them for its own purposes since long before Sun or anyone else did. Whether the patent will cause issues for other vendors has yet to be seen, as no infringement suits have been filed yet.

But for all this activity, mobile data centers aren’t exactly selling like hotcakes; Sun announced its first customer in June 2007, and Rackable hasn’t disclosed any, other than saying they have some.