I have, in the last few days, changed my 2 x 250 GB IDE drives for 2 x 1 TB SATA drives.
One drive is used once a day to mirror the other. Previously I used hdparm to spin down the mirror drive after a short period of inactivity and I've tried to do the same with one of the new drives but I suspect it isn't working.
If I issue the command 'sg_start --stop /dev/sdb' I hear a click from the computer as if the drive is being switched off but can't detect any difference in noise. That could be because the drive is ultra quiet but if I then try to mount a partition on the drive it mounts instantly. With the previous drives if I did that there would be a significant pause whilst the drive was spinning up to running speed.
Does the fact that there is no pause of any sort when mounting the drive mean that it hasn't stopped?
I've also tried 'sdparm --command=stop /dev/sdb' with the same results. If I issue the command sdparm --command=ready /dev/sdb then it comes back with 'ready'.