Facebook Achieves Power Efficiency with Cold Storage

Facebook is now operating modified Open Rack designs in its Cold Storage data center facility in Prineville, Oregon, which preserves the billions of photos shared by its users.

The modified Open Rack architecture packs 2 PB storage (using 4 TB drives).  Facebook has achieved one-quarter the power usage of conventional storage servers, according to the company's engineering blog. Because this facility is used for cold storage rather than live streaming, Facebook was able to remove all redundant electrical systems, including all uninterruptible power supplies (DCUPS) and power generators.

In  addition, rather than storing multiple copies of the data in different hardware failure domains, Facebook is now implementing a Reed Solomon Redundancy technique to store fewer than two copies of the same data but still protect against loss should a hardware failure occur.  The technique involves cutting the data up into small pieces and using Reed-Solomon error correction codes to generate additional sets of blocks for file reconstruction.

Facebook's blog posting notes that its two cold storage data facilities are now protecting hundreds of petabytes of data.

https://code.facebook.com/posts/1433093613662262/-under-the-hood-facebook-s-cold-storage-system-/