Facebook has a lot of photos. Actually, Facebook has a huge amount of photos, much more than anything else online, more than several photo sharing or hosting sites put together.
So many that Facebook doesn't know what to do with them, it's building new data centers to store all of its data, but much of this data is made up of photos, thousands for each Facebook users, photos that people rarely access in any given day.
Which is why Facebook is looking to build some cold storage facilities to archive all the billions of photos nobody cares about, or, put another way, which people only look at every Christmas or so.
Cold storage servers differ from regular servers in that, as the name suggests, they're designed for long-term storage and not immediate access.
Data that doesn't need to be available all the time and that is accessed rarely is stored on these servers which are designed for capacity and efficiency, rather than speed or latency.
Facebook's cold storage servers will have eight times more storage capacity than its regular servers, but will use up only 20 percent of the energy since they'll be in standby for most of the time.
Eight percent of the photos Facebook holds generate 82 percent of the traffic. The long tail is incredibly long in this case.
The downside is that these infrequently accessed photos are going to take longer to load. Most people shouldn't actually notice, even in the cold storage servers, access time should be in the order of seconds at most.
Each of the three facilities Facebook has planned will be able to store 1 exabyte of data, as much as one million 1 TB hard drives found in regular computers.