IBM 704 - Manual (Page 278)

Troubleshooting
The following table describes the SCSI drive status conditions that
the LEDs indicate.
Power
On LED
Drive
In-Use
LED Drive
Fault
LED Status
On Off Off Hot-swap drive is present;
power to the drive is on.
On Blinking Off Hot-swap drive is present;
power to the drive is on. The
drive is in use.
Off Off On The drive has a problem, and
can be replaced.
On Off Blinking
slowly Disk-array models only: The
drive should not be replaced at
this time. The drive has just
been replaced, and the disk
array is being rebuilt. Power
to the drive is on.
Off Off Off No drive is installed in the
bay.
If a drive is present, but the
LEDs are off, check the cable
connections to the SCSI
backplane.
260 PC Server 704 User's Handbook