another question: what is the difference in power consumption between a HDD that's powered up but idle, and one that's being used to read from or write to? As

another question: what is the difference in power consumption between a HDD that's powered up but idle, and one that's being used to read from or write to? As an aside, erasure codes allow you to reduce power consumption as the redundant fragments are only necessary for safety, not for regular retrieval. You don't need glacier to benefit from that. (But glacier might be an optimization of that strategy)