Unable to stop drive

Error detaching: helper exited with exit code 1: Detaching device /dev/sdb
USB device: /sys/devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2)
SYNCHRONIZE CACHE: synchronize cache(10):  Fixed format, current;  Sense key: Key=9
 Additional sense: Logical unit not ready, cause not reportable
  Info fld=0x0 [0]
FAILED: No such file or directory
(Continuing despite SYNCHRONIZE CACHE failure.)
STOP UNIT: start stop unit: transport: Host_status=0x07 [DID_ERROR]
Driver_status=0x00 [DRIVER_OK, SUGGEST_OK]

FAILED: No such file or directory