I talked to them at the Open Compute Summit and got the chance to look at it up close. They quoted me 100GB/disc and 10,000 discs in the cabinet for 1PB. They could have been rounding those numbers for simplicity, but that gets you in the neighborhood.

From the video: 24 magazines/rack * 36 cartridges/magazine * 12 discs/cartridge * 50 GB/disc = 518TB/rack. Based standard dual-layer discs. I cannot comment on storage of our traditional spinning-disk racks.

A comment on the video suggested 950 TB per rack.

> 1 Rack = 44 magazines; 1 magazine = 36 cartridges; 1 cartridge = 12 blueray discs. So, ~950TB.

If they use 128 GB Blu-Ray disks its about 1.26 PB per rack.

24 mag -> 36 cart -> 12 disks

10,368 Disks in total per rack