Technical data

• A storage array with dual-redundant HSG60 or HSG80 controllers in
multiple-bus failover is four targets and consumes four ports on a switch.
• The HSG60 and HSG80 documentation refers to the controllers as
Controllers A (top) and B (bottom). Each controller provides two ports
(left and right). (The HSG60 and HSG80 documentation refers to these
ports as Port 1 and 2, respectively.) In transparent failover mode, only
one left port and one right port are active at any given time.
With transparent failover enabled, assuming that the left port of the top
controller and the right port of the bottom controller are active, if the top
controller fails in such a way that it can no longer properly communicate
with the switch, then its functions will fail over to the bottom controller
(and vice versa).
• In transparent failover mode, you can configure which controller
presents each HSG60 or HSG80 storage element (unit) to the cluster.
Ordinarily, the connections on port 1 (left port) have a default unit offset
of 0, and units designated D0 through D99 are accessed through port 1 of
either controller. The connections on port 2 (right port) have a default
unit offset of 100, and units designated D100 through D199 are accessed
through port 2 of either controller.
• In multiple-bus failover mode, the connections on all ports have a default
unit offset of 0, and all units (D0 through D199) are visible to all host
ports, but accessible only through one controller at any specific time. The
host can control the failover process by moving units from one controller
to the other controller.
• The Fibre Channel Tape Controller, Fibre Channel Tape Controller II,
TL891, TL895, and ESL9326D are supported on a Fibre Channel storage
bus. For more information, see the
Enterprise Backup Solution with
Legato NetWorker User Guide. Legato NetWorker Version 6.0 is required
for application failover.
• Tapes are single-stream devices. There is no load balancing of I/O
requests over the available paths to the tape devices. The first available
path to the tape devices is selected for I/O.
2.3.2 KZPSA-BB SCSI Adapter Restrictions
KZPSA-BB SCSI adapters have the following restrictions:
• The KZPSA-BB requires A12 firmware.
• If you have a KZPSA-BB adapter installed in an AlphaServer that
supports the bus_probe_algorithm console variable (for example, the
AlphaServer 800, 1000, 1000A, 2000, 2100, or 2100A systems), you must
set the bus_probe_algorithm console variable to new by entering the
following command:
Hardware Requirements and Restrictions 2–9