Only a fraction of Facebook's hundreds of billions of photos are viewed regularly, while the rest languish pages deep in our profiles. These older images are rarely seen, but they still take up vital space on the company's servers. Facebook has been searching for a new, more efficient way to store such pictures. Early last year, the company called for a new type of low power flash memory that would allow infrequently accessed data to be held in cold storage. Now Facebook has turned to another technology to store its information: Blu-ray discs.

The company has built a prototype system that uses 10,000 Blu-ray discs to store a petabyte of data. Speaking at this year's Open Compute Summit, Facebook's vice president of engineering, Jay Parikh, said the new system would save Facebook 50 percent in costs and 80 percent in energy usage over existing hard-disk cold storage methods used to store rarely accessed files. Facebook's engineering department yesterday released a video explaining how the system uses a robot arm to pick specific data discs from cartridges held within larger magazines. The design for the storage system is likely to be made public through the Open Compute Project, but that for now, Facebook is reportedly still deciding which portions of the build it will submit.

Facebook still eventually hopes to use low-power flash memory for storage

Parikh said the prototpye Blu-ray system is already in use, and can store up to 30 petabytes of data. According to GigaOm, a second site will come online soon. Facebook intends such facilities to store up to 150 petabytes of data within a few months, only a small portion of the 3 exabytes the sites are designed to store. But even as it rolls out production of its new Blu-ray servers, Facebook is continuing to look for alternate options for low power data storage. IDG News Service reports the company eventually hopes to use low power flash memory to store the world's rarely viewed photos, but the prohibitive cost means it'll have to be"the worst flash possible."