> Have you ever computed how much power you would save if you turned them off when not needed?
Electrical power is a gigantic part of our datacenter bill (like 60%). However, we cannot really ever turn off the hard drives.
If they were powered down, it would take too long to retrieve data. It would be like Amazon Glacier where it can take 15 minutes to get a single image back.
> is every pod constantly in use?
The way we built it, yes. If one user deletes a backup or unsubscribes from the Backblaze service, it frees a little bit of space on pods all over the datacenter. So we allow some other customer to use that space up as soon as we can.
We also use ALL the pods in the datacenter to give us "breadth" to accept data faster. This is particularly helpful on surges of new customers due to a press event, or if a competitor like CrashPlan decides to exit the market.