Project Natick's Northern Isles datacenter is partially submerged and cradled by winches and cranes between the pontoons of an industrial catamaran-like gantry barge.
The second phase will test the feasibility of deploying a larger model - 12.2 m in length and 2.8 m wide - which contains 864 data center servers and 27.6 petabytes of disk.
Engineers slide racks of Microsoft servers and associated cooling system infrastructure into Project Natick's Northern Isles datacenter at a Naval Group facility in Brest, France.
According to the release, their goal is to create "self-sufficient underwater data centers that can deliver lightning-quick cloud services to coastal cities" using "experimental, shipping-container-sized" prototypes.
"The world's oceans at depth are consistently cold, offering ready and free access to cooling, which is one of the biggest costs for land-based datacenters", the release said.
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This is a really small data center but the number of servers should be enough to provide Microsoft with data to see if scaling up the project makes sense. And EMEC has been experimenting with tidal and wave energy for 14 years, with one of its test sites on the beach where the Project Natick cable comes ashore.
More than half of the world's population lives within about 120 miles of the coast.
Microsoft said that while the first Project Natick test was to see if it was possible to operate an undersea data center, the second test is meant to learn if the "concept is logistically, environmentally and economically practical". "It's our belief that this type of data center could lead to reduced costs, and simpler structures that incorporate fewer materials, requiring less maintenance and electricity", a Microsoft spokesperson said.
If the idea ever reaches commercial scale, the underwater data centers will probably be powered by whatever energy source is available locally.
The hope is that it won't need as much fixing as a traditional data centre anyway, as the server submarine they're sinking will have most of the oxygen and moisture taken out of its atmosphere, hopefully reducing corrosion.