said by yyzlhr:
Out of curiosity, do you know why it's necessary for the hard drive to be running when the STB is powered off and not recording anything? I noticed Rogers is not the MSO that leaves the hard drives spinning all the time and I've never understood why.
When you press the power button on a modern set top, it's not really powered off. Often just the front lights turn off and it doesn't shut most of the components off. For a PVR, it has to be constantly running in order to start a recording at the correct time. If it was completely shut down, meaning the operating system running on it(ones I used ran a stripped down version of linux) was not started, then when the PVR needed to record something, it'd take many minutes to start and you'd possibly miss the start of the recording.
Realistically the set top is in an on state all the time. The drive spinning down is supposed to save you electricity, but it'll spin back up whenever something needs to read or write to it.
Something must be reading or writing to the hard drive every few minutes which causes it to spin back up. This could be the PVR scheduler checking the recording database, or something syncing it's state with a database on the drive.