Controlling power settings for external USB disk drives using sdparm

[Jesse Molina <jesse@opendreams.net>]

Hi everyone

I wanted to post, for posterity, what I recently learned while playing 
with my new external USB3 disk drive.

I needed to control the power settings for this drive. I noticed that it 
was never ever spinning down, so I wanted to be able to either power in 
up/down on command, or have it automatically spin down after a period of 
inactivity. In the end, I was able to do both.

My device is a Seagate ST4000DM000. This should probably work for 
similar Seagate enclosures, like the STEB2000100, STEB3000100, and 
STEB5000100.

I wasn't able to get hdparm to work with my device at all, but that 
should probably be your first step. See if "hdparm -i" works, then do a 
-I, then try setting the spin-down with -S.

I had to use the sdparm tool instead, and the notes here reflect what 
worked for me.

WARNING: Use the /dev/disk/by-id path for USB devices, not letter-device 
path like the sdb example I used below.

# Show your disks and devices
        udisksctl status
        udisksctl info -b /dev/sdb

# Interogate the device to collect info:
        sudo sdparm --flexible -6 -l -i /dev/sdb
        sudo sdparm --flexible -6 -l -i -a /dev/sdb

# Show all of the parameters/settings:
        sudo sdparm --flexible -6 -l -a /dev/sdb

# Immediately start and stop the disk:
        sudo sdparm --readonly --command=stop /dev/sdb
        sudo sdparm --command=start /dev/sdb
        # Per the hdparm man page, It may be necessary to mark the disk 
as "offline" with:
        #       sudo bash -c 'echo offline > /sys/block/sdb/device/state'
        # Normalize with:
        #       sudo bash -c 'echo running > /sys/block/sdb/device/state'

# Get the auto-spindown parameter current settings:
        sudo sdparm --flexible -6 -l --get SCT /dev/sdb
        sudo sdparm --flexible -6 -l --get STANDBY /dev/sdb
        # SCT = spindown timer in 100 miliseconds.
        # NOTE: The sdparm man page says SCT is measured in 100ms. but 
for my Seagate drive, it's actually 1=50ms.
        # STANDBY = the spindown timer on/off switch. 0=off (never spin 
down), 1=on (spin down to timer)
        # These were my default values on my ST4000DM000:
        #  STANDBY     0  [cha: y, def:  1, sav:  1]
        #  SCT       4294967286  [cha: y, def:9000, sav:9000]
        # This means the device NEVER spins down by default.

# Set the auto-spindown parameters to spin down after 15 minutes of 
inactivity (assuming SCT=50ms instead of 100ms):
        sudo sdparm --flexible -6 -l --set SCT=18000 /dev/sdb
        sudo sdparm --flexible -6 -l --set STANDBY=1 /dev/sdb
        # NOTE: this these settings are lost on reboot.

# Set the auto-spindown parameters to spin down after 15 minutes of 
inactivity (assuming SCT=50ms instead of 100ms):
        sudo sdparm --flexible -6 -l --save --set SCT=18000 /dev/sdb
        sudo sdparm --flexible -6 -l --save --set STANDBY=1 /dev/sdb
        # NOTE: Values will be saved to the device and *should* be 
retained between reboots and host moves.
        # NOTE: My Seagate ST4000DM000 failed to save settings. Seagate 
sucks. Whatever.



Finally, I put this in my /etc/rc.local to set on boot:

sdparm --flexible -6 -l --set SCT=18000 --set STANDBY=1 /dev/sdb


I hope this helps someone. The HOWTOs and examples I found while 
searching the internet didn't really help me that much. I had to do a 
lot of experimenting before I discovered that this device would not 
really talk to me without "--flexible -6" being set, and that 
"--readonly" was required with the stop command (or it just spun right 
back up).

If you have any feedback or corrections, let me know!