hdparm -B 255 /dev/sdb
/dev/sdb:
setting Advanced Power Management level to disabled
HDIO_DRIVE_CMD failed: Input/output error
The one thing you can do though is to set hdparm spindown time lower (it doesn't seem to work that well).
-S set standby (spindown) timeout
hdparm -S 251 /dev/sda
/dev/sda:
setti........