HP LTO Ultrium Technical Reference Manual page 26

LEDs Cause
Ready ON.
The drive is ready for operation.
Ready FLASHING.
The drive is carrying out a normal activity
(read, write).
Ready FLASHES twice, then pauses ON,
then FLASHES twice.
The drive is in OBDR mode.
Ready FLASHING fast. (Other LEDs may be
on or flashing.)
The drive is downloading firmware.
Ready OFF, others ON.
Firmware is being reprogrammed.
26 Front panel and LEDs
Action required
None. This is normal.
None.
If the drive is upgrading firmware, do not
reset or power cycle it.
If you need to exit OBDR mode, power cycle
or reset the drive.
NOTE:
OBDR is not supported in all versions of
the drive.
None.
Do not reset or power-cycle the drive.
None.
Do not reset or power-cycle the drive.