HP StorageWorks 2500 Disk System - Manual (Page 19)

I/O modules
Two I/O modules provide an interface between the disks and the host system. The I/O modules are used
to route data to and from the disks in a dual-loop configuration to eliminate a single point of failure.
Each disk drive is connected to both I/O module A and I/O module B (
Figure 4 -3). Each I/O module is
connected to an independent, external FC loop. I/O module A connects to loop A, and I/O module B
connects to loop B (see Figure 1 on page 14).
CAUTION:
Keep the loops completely separate to ensure that the failure of a single component (I/O module,
transceiver, or cable) does not stop data transmissions to active drives.
25175a
1 2 3 4 5
1. FC loop B 4. I/O module A
2. I/O module B 5. FC loop A
3. FC disks (3 are shown, but up to 14 disks are supported in each DS2500)
Figure 4 Redundant disk connections
The operation and function of both I/O modules are identical. Each I/O module has two ports that
can transmit and receive data for bidirectional operation. Port use and connections are configuration
dependent (see " Cables and cabling " on page 24). Each port is identified with a transceiver element
number, and its status is displayed on an LED ( Figure 5 ). Port 1 is the bottom loop port, and port
2 is the top loop port.
• Port 2 LED—On indicates that a signal was detected at the top transceiver.
• Power LED—On indicates that power is present on the I/O module.
• Port 1 LED—On indicates that a signal was detected at the bottom transceiver.
2500 Disk System user guide 19