User`s guide

Figure 1–2 Dual-Redundant HSJ30 Array Controller Subsystem—Block Diagram
HOST
CPU
STAR
COUPLER
READ OR
WRITE-
BACK
CACHE
FAILOVER COMMUNICATION
HSJ30
CONTROLLER
HSJ30
CONTROLLER
EIA-
423
PORT
EIA-
423
PORT
MAINTENANCE
TERMINAL
MAINTENANCE
TERMINAL
(OPTIONAL)(OPTIONAL)
CI
CI
CI
CXO-3699D-MC
112233
READ OR
WRITE-
BACK
CACHE
• Each SCSI–2 port supports up to six (or seven) SCSI–2 devices,
3
, depending
on the subsystem configuration.
• The three SCSI–2 port cables from the controller shelf can be routed to
more than one storage shelf as desired, taking into consideration prescribed
configuration rules and restrictions as listed in Chapter 3.
The HSD30 array controller consists of a single module that can be configured
alone (nonredundant) (with its cache module) or with a second HSD30 controller
module (with its cache module) for dual-redundant availability.
The HSD30 array controller host port is an 8-bit wide DSSI interface. The
HSD30 array controller requires a DSSI trilink connector block (Digital part
number 12–39921–02) mounted on its host connector (which is included with each
controller), and requires external terminators (Digital part number 12–31281–01)
as appropriate. (See Section 4.6.2.2 for installation instructions for DSSI host
port cables.)
3
An HSD30 dual-redundant controller configuration supports up to 18 devices. Lower
availability configurations can support up to 21 devices (seven per SCSI–2 port) but this
will sacrifice a convenient upgrade to any of the possible higher availability options,
such as redundant power.
Introduction to HS Array Controllers 1–5