Yesterday, we reported that Facebook has worked out an extremely cost-efficient solution for keeping data that’s rarely accessed, known as “cold storage.”
Rather than using hard drives, flash storage, or old-fashioned tape drives, Facebook’s design relies on a whopping 10,000 Blu-ray discs to store one petabyte — that’s a million gigabytes — of things like duplicates of user photos and videos.
Today, the company pointed us to a video put together by the Facebook Engineering team showing off the prototype of their new design:
Post by Facebook Engineering. Since it's using over 10,000 individual discs -- each rack has 24 magazines, which each hold 36 cartridges, each of which contains 12 Blu-ray discs -- the system required a mechanical method to quickly sort through all of them. Since it's data that isn't being accessed frequently, they also had to be able to do it without wasting a ton of power. [image url="http://static.businessinsider.com/image/52eaba0c6bb3f7c73b631ee9/image.jpg" alt="Facebook backup robot" link="lightbox" size="secondary" align="right" clear="true" source="Facebook Engineering" caption="It may not look fancy, but this little robot yields Facebook huge power savings."] The solution is like one of those Redbox DVD rental machines on steroids. A robot built into the center of the storage rack can be told what data needs to be looked at and pull out the single disc among thousands that contains it nigh-instantly. More impressively though, Facebook Director of Hardware Engineering Giovanni Coglitore claims that when it isn't actively searching for data on a disc, the system drops down to a state of "virtual zero" power usage. That last point is huge. Rather than constantly keeping a hard drive powered on, they only have to look at a disc when it's needed. That lets them reduce power usage by 80% compared to traditional storage. There's another advantage to using optical discs like Blu-rays for this kind of storage instead of traditional hard drives: they're far more reliable. Coglitore states that the discs the company is using are certified for 50 years of use, several times greater than drives with spinning mechanical parts that can fail unpredictably and are essentially expected to break down with use. Plus, by separating the drive that reads and writes data and the media containing data, a drive failure doesn't mean data loss. That greatly reduces the impact of failures when they do occur: all of the information they're storing is still safe, so all they have to do is swap out the failed part and move on. [image url="http://static.businessinsider.com/image/52eac249eab8ea2c30e46802/image.jpg" alt="Facebook storage" link="lightbox" size="secondary" align="right" clear="true" source="Facebook Engineering" caption="A magazine of Blu-rays being ejected for 'colder' storage."] Since it's meant for storing data that people don't access often, the system is also designed to move data to "even colder" storage when capacity in a rack is running low or a particular set of data is particularly unused. While Facebook's Blu-ray storage system is likely a temporary solution until cheap, low-powered flash storage is available, the company has stated that it will go into production tests later this year and may expand the system to accommodate up the five petabytes of storage.
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