Disk Spin down (Tested with Bullseye 2022)
Even though everything concerning block devices in linux has shifted to unique identifiers, hdparm has not, and will still use the old /dev/sdx system
To control disk spindown, and to manually issue commands, you will need to have the package installed
apt-get install hdparm
There is a probelm with disk spindown via hdparm, the problem is that you must address a disk as /dev/sdc , which changes in the case of USB media and other disks, even when you add slaves,
hdparm -Y /dev/sdb will spin a disk down instantly
hdparm -S 240 /dev/sdb will set this disk to sleep when idle for 20 minutes (5 second units here)
or adding at the bottom of the file /etc/hdparm.conf a section such as
/dev/sdc {
spindown_time = 240
}
to make those changes persistent across reboots.
To check the status of a disk, here is what you do
hdparm -C /dev/sde
You could get one of the following results
When spun down…
drive state is: standby
When active
drive state is: active/idle
Don’t make your disks spin-down too often, 20 minutes is good for me almost in all circumstances.
If the disks don’t spin down, chances are that selftest is enabled…
Check if it is enabled with
smartctl -a /dev/sdb
if it reads
Auto Offline Data Collection: Enabled.
then you need to disable it with
smartctl --offlineauto=off /dev/sdb
then wait for them to finish (if a test is running) then spin down.