Short description:
External usb drive bay:
Bus 001 Device 002: ID 13fd:1840 Initio Corporation Shintaro SH23SDOCK Hard Drive Docker
Disk (as identified by smartctl -a /dev/sdb -d sat -T permissive):
Model Family:     Toshiba 2.5" HDD MK..52GSX series
Device Model:     TOSHIBA MK2552GSX
Firmware Version: LV011C

hdparm -Y /dev/sdb
Disk spins down, waits some time, then spins up again
and hdparm prints an error:
HDIO_DRIVE_CMD(sleep) failed: Invalid argument

I see in source code that _two_ commands are issued to the drive:

if (do_drive_cmd(fd, args1)
         && do_drive_cmd(fd, args2)) {
            err = errno;
            perror(" HDIO_DRIVE_CMD(sleep) failed");
        }

I have replaced this with quick&dirty

do_drive_cmd(fd, args1);

.. and my disk spins down OK.
What does the second command do?

Regards,

Dominik Ałaszewski