Facebook has developed a prototype storage system that uses a 7 feet tall cabinet filled with 10,000 Blu-ray optical discs to store one Petabyte of data. The company is planning to use this cold storage system to store rarely accessed files, such as backups of users' photos and videos.

Blu-ray discs are ideally not used for primary storage because data retrieval is slow, but they are a good option for maintaining backups, especially if you consider the cost factor. According to Facebook's vice president of engineering, Jay Parikh, who was speaking at this year's Open Compute Summit, the new storage system would save Facebook 50 percent in costs and 80 percent in energy usage when compared to standard HDD cold storage techniques.

Parikh showed the prototype system on stage at the summit. From outside, it looks like any other server cabinet, but it uses a robotic arm inside to move the discs around. Facebook also released a video explaining how the system works.

Although the design of the storage system would be made public through the Open Compute Project, it is still not clear which portions of the build Facebook will submit to the project.

The prototype Blu-ray system is apparently already in use, and has 30 Petabytes of storage capacity. According to a GigaOm report, a second such resource will be online soon. The company expects to expand the storage capacity to 150 Petabytes within a few months.

Blu-ray is just an option for the cold storage, according to IDG News, Facebook is eventually eyeing a version based on low-power flash storage.