Their Q3 2018 stats had a bit of info on the lifecycle of introducing new disks: https://www.backblaze.com/blog/2018-hard-drive-failure-rates/ https://www.back

Their Q3 2018 stats had a bit of info on the lifecycle of introducing new disks: https://www.backblaze.com/blog/2018-hard-drive-failure-rates/ https://www.backblaze.com/blog/2018-hard-drive-failure-rates... > In Q3 we added 79 HGST 12TB drives (model: HUH721212ALN604) to the farm. While 79 may seem like an unusual number of drives to add, it represents “stage 2” of our drive testing process. Stage 1 uses 20 drives, the number of hard drives in one Backblaze Vault tome. That is, there are are 20 Storage Pods in a Backblaze Vault, and there is one “test” drive in each Storage Pod. This allows us to compare the performance, etc., of the test tome to the remaining 59 production tomes (which are running already-qualified drives). There are 60 tomes in each Backblaze Vault. In stage 2, we fill an entire Storage Pod with the test drives, adding 59 test drives to the one currently being tested in one of the 20 Storage Pods in a Backblaze Vault.