Using Blu-ray for corporate data storage is a relatively new idea and won't necessarily be a good storage method for all businesses. So why would Facebook choose this technology over more established ones?
It has been reported that Facebook is testing an optical Blu-ray disk library in the first instance to store its compliance data. Blu-ray supports both re-writeable as well as WORM (write once, read many times) media. Data on WORM discs cannot be modified - only the disk itself can be destroyed - and WORM media types are therefore ideally suited to storing information that must be maintained in its original state, such as compliance and regulatory data.
The downside is that capacity once used cannot be reused and so it is unsuitable for any data that is required by regulation to be able to be deleted (user accounts and content) and is by definition always used to store inactive data.
Facebook is initially looking at using 1PB of capacity for cold storage - data that can be filed away that doesn't require accessing on a regular basis - which for the social network includes duplicates of user videos and photos kept for backup purposes. In terms of suitability for the task, Blu-ray potentially passes the test. But what about costs?
The Blu-ray prototype contains approximately 10,000 optical discs and a petabyte of data in a rack-sized cabinet. In the following table, you can take a look at the specifications and approximate costs of a Blu-ray system versus an LTO tape library solution. Through this analysis, we found that tape can actually cost up to 95 per cent less than Blu-ray and at the same time take up half the rack space needed for the same storage capacity.
N.B. This table of analysis is based on the following assumptions:
- The cost of the sheet metal, power, fans and robotics required for one rack is assumed to be about equal between tape and Blu-ray
- The cost of the media is based on Internet research to find approximate lowest online pricing
- The cost of the drives is not included because pricing is so variable depending on the source and in the big picture, the drive cost is dwarfed by the cost of the media
As the table also shows, we found that tape transfers data up to six times faster per drive and 20 times cheaper than Blu-ray. While our analysis is based on some assumptions noted above, it is very clear that tape has a clear cost and performance advantage for storing data for long periods of time. Tape may be one of the oldest forms of technology, but tape innovation and large volumes of data growth in the market have resulted in an increase in the demand for tape in large-scale, long-term archives.