Facebook Experimenting With Blu-ray As a Storage Medium 193
s122604 links to CNN's explanation of what may be the future of cold (or at least lukewarm) storage at Facebook, which is experimenting with massive arrays of Blu-Ray discs for seldom-accessed user files. Says the report: The discs are held in groups of 12 in locked cartridges and are extracted by a robotic arm whenever they're needed.
One rack contains 10,000 discs, and is capable of storing a petabyte of data, or one million gigabytes.
Blu-ray discs offer a number of advantages versus hard drives. For one thing, the discs are more resilient: they're water- and dust-resistant, and better able to withstand temperature swings. Their data can be restored more quickly, and they're easier to transport.
Most important, though, is cost. Because the Blu-ray system doesn't need to be powered when the discs aren't in use, it uses 80% less power than the hard-drive arrangement, cutting overall costs in half.
Everything old is new again. (Score:5, Informative)
Enterprises have been doing this with tape for 30 years.
In fact, modern tape technology probably has a higher "volumetric" density than BD.
Re:Why not just use hard drives and then store... (Score:5, Informative)
They'd also be cheaper, even at the bulk HDD rate that FB would pay.
A quick on-line search show a spindle of fifty 50GB Blu-Ray discs (2.5 TB) retails for about $100. A 4TB HDD costs about $140. So HDD is actually cheaper per byte of storage. Maybe wholesale price ratios are way different from retail, but I see no reason to assume that. So BluRay doesn't win on price, volume, or access speed. The concerns about moisture and big temperature swings seems odd. Are Facebook data centers exposed to the weather?
Backup, not storage (Score:4, Informative)
I read TFA. They're not using them as "storage" in the sense of active, accessible storage. It's a backup system.
What they're trying is, instead of storing redundant copies of everything on multiple drives (for resilience and geolocality), they're keeping one copy live and keeping backups on blu-ray.
So there's never a latency of minutes while it loads data from Blu-Ray, you just might be routed to Siberia or something to get the one active copy. If that copy's bad, error (restore from backup during next nightly batch or something).
Re:Why not just use hard drives and then store... (Score:5, Informative)
So HDD is actually cheaper per byte of storage.
If the HD needs to be replaced much more frequently than the Blu-Ray media the advantage switches quite quickly. For example, if the HD is replaced every 5 years and the Blu-Ray media is replaced every 20 years the HD would have to cost 1/4 of the Blu-Ray to match the hardware price.
The concerns about moisture and big temperature swings seems odd.
Temperature and humidity control are very expensive as it takes a lot of electricity. If the media can handle higher temperature and humidity swings then operation costs will be much lower.