Technical data

3.8 Connecting Systems Into a DSSI VAXcluster

Conﬁguration

Note

A DSSI VAXcluster conﬁguration is supported only under VMS Version

5.5-1HN or later.

A DSSI VAXcluster conﬁguration consists of two or more systems conﬁgured

as a DSSI VAXcluster and sharing their DSSI devices through a Digital

Storage System Interconnect (DSSI) bus. See Figure 3–8 and Figure 3–9 for

connections. Each system can have direct access to any of the devices on the

DSSI bus, including a shared system disk.

The simplest DSSI VAXcluster conﬁguration, a two-system conﬁguration, can

let one system disk be used as the system disk for both systems. Although the

system disk resides in one system, both systems have equal access to it and to

any other DSSI storage device in either system.

A DSSI device, such as the RF35, has a built-in DSSI VAXcluster capability

that can dynamically serve two or more systems. DSSI adapters, embedded in

the system CPU, let you extend a DSSI bus by connecting it to another system.

Using an external DSSI cable, DSSI-based systems can be connected to form a

DSSI VAXcluster conﬁguration.

The beneﬁts of a DSSI VAXcluster conﬁguration:

• VAXcluster features such as shared data across systems and satellite nodes

are available to you.

• Higher system availability — If one of the systems is unavailable due to a

system malfunction, the satellites booted through it can continue operating

through the other system.

If one system fails, all satellite nodes booted through that system lose

connections to the system disk. Each satellite knows that the system disk

is available through a second path. The satellite nodes establish a new

connection through the other system and continue operation.

To increase system availability, a second system disk can be added to each

boot node. If one system disk fails, the other system disk continues to serve

one system and the satellite nodes booted through it. As in any VAXcluster, a

second system disk improves availability but increases system management

tasks.

3–16 Network Information