User`s guide

• Connectivity functions:

A second controller can be connected to a single controller conﬁguration to

allow failover support of attached devices in the event of a controller failure.

This is called a dual-redundant conﬁguration.

EIA–423 compatible terminals can be connected to each controller’s

maintenance terminal port. A VAXcluster™ console system (VCS) or

serial interface also can be connected to the maintenance terminal port

for maintenance and installation.

• RAID level 0, 1, 0 & 1, 3, and 5 functionality is supported and is described

in Chapter 6 of this manual.

2.3 What Is Failover?

The following sections describe what failover is and how it works. For more

information about the SET FAILOVER and SET NOFAILOVER commands, see

Appendix B.

Failover is the ﬁrmware process that takes place when one HS controller fails

in a dual-redundant controller conﬁguration. In a failover (dual-redundant)

conﬁguration, information is shared between the two controllers, such as:

• Storageset names (for example, mirrorsets, RAIDsets, and stripesets)

• Actual device conﬁguration (PTL descriptions) and the association to named

storagesets

• Logical unit deﬁnitions

Note

Both HSZ array controllers in a dual-redundant pair ‘‘know about’’ each

other’s SCSI target IDs, but do not share them.

For HSJ and HSD30 array controllers: Prior to failover, all resources are

considered available to both controllers until a logical device is brought online by

a host through one of the controllers. At this point, all containers used by the

logical device become solely accessible through the one controller.

For HSZ array controllers: Prior to failover, resources are always accessible

only to a particular controller because the controller is a SCSI target of the host,

and LUNs must be visible through a single target ID. This is true whether or not

a unit is currently interacting with the host.

In a failover conﬁguration, all commands are shared between the two controllers

with the exception of the following commands:

SET THIS_CONTROLLER

SET OTHER_CONTROLLER

SHOW THIS_CONTROLLER

SHOW OTHER_CONTROLLER

RESTART THIS_CONTROLLER

RESTART OTHER_CONTROLLER

SHUTDOWN THIS_CONTROLLER

SHUTDOWN OTHER_CONTROLLER

CLEAR INVALID_CACHE THIS_CONTROLLER

CLEAR INVALID_CACHE OTHER_CONTROLLER

2–16 Controller Technical Description