45xx Modular Disk Subsystem Manual for G-Series Releases

Introduction
45xx Modular Disk Subsystem Manual for G-Series Releases—142466
1-8
Back-End Boards (BEBs)
Disk Drive Specifications
Although some specifications of individual disk drives used in the 45xx modular disk
subsystem might differ slightly, Table 1-4 shows the specifications that are typical.
Back-End Boards (BEBs)
The disk drives in a 45xx disk module communicate with a 6760 adapter through a
back-end board (BEB). There are two BEBs in each 455mod8 module and one BEB in
each 455DS module. A BEB translates fiber-optic signals from the 6760 adapter into
SCSI commands and data for the disk drives. A BEB plugs in to one of the two slots in
the back section of a module. The BEB slots are visible only when the fan CRU is
removed.
BEB LEDs
A BEB has three indicator LEDs, one green and two amber-orange (shown in Figure 1-4
on page 1-9):
•
The green LED indicates when the BEB is powered on, and it is normally lit. You
can use the TSM FLASH command to flash the green LED on and off, which can
help you find or identify a particular BEB.
•
The amber-orange LED in the middle of the three BEB LEDs indicates the presence
of a fiber-optic signal, and it is lit when the BEB is receiving a fiber-optic signal.
•
The amber-orange LED on the end, when lit, indicates error conditions.
For troubleshooting a BEB using the BEB LEDs, see Section 3, Checking Hardware
Operation.
Table 1-4. Disk Drive Specifications
Characteristic 4560 4570 4580 4590
Storage capacity, formatted (GB) 2.0 4.2 8.8 17.9
Form factor (inches) 3.5 3.5 3.5 3.5
Average seek time (ms) 10 10 10 8
Rotational speed (rpm) 5400 7200 7200 7200
Average rotational latency (ms) 5.6 4.1 4.1 4.1
Data transfer rate (MB per second) 5 5 5 5
Buffer size (KB) 256 512 512 1024
Note. If one BEB in a 455mod8 module fails, the disk drives in the module can still
communicate with the Tandem host through the other BEB in that module.