Technical data

System Management Features

4.9 OpenVMS Cluster Systems

Conﬁgurations that use Fibre Channel fabrics can be extremely large. Distances

up to 100 kilometers are supported in a multisite OpenVMS Cluster system.

OpenVMS supports the Fibre Channel SAN conﬁgurations described in the

Compaq StorageWorks Heterogeneous Open SAN Design Reference Guide,

available at the following Compaq web site:

http://www.compaq.com/storage

Enabling Fast Path for Fibre Channel can substantially increase the I/O

throughput on an SMP system. For more information about this new feature, see

Section 4.9.2.

Prior to OpenVMS Alpha Version 7.3, I/O requests larger than 127 blocks were

segmented by the Fibre Channel driver into multiple I/O requests. Segmented

I/O operations generally have lower performance than one large I/O. In OpenVMS

Version 7.3, I/O requests up to and including 256 blocks are done without

segmenting.

For more information about Fibre Channel usage in OpenVMS Cluster

conﬁgurations, refer to the Guidelines for OpenVMS Cluster Conﬁgurations.

4.9.4.1 New Fibre Channel Tape Support (Alpha)

Fibre Channel tape functionality refers to the support of SCSI tapes and SCSI

tape libraries in an OpenVMS Cluster system with shared Fibre Channel storage.

The SCSI tapes and libraries are connected to the Fibre Channel by a Fibre-to-

SCSI bridge known as the Modular Data Router (MDR).

For conﬁguration information, refer to the Guidelines for OpenVMS Cluster

Conﬁgurations.

4.9.5 LANs as Cluster Interconnects

An OpenVMS Cluster system can use several LAN interconnects for node-to-node

communication, including Ethernet, Fast Ethernet, Gigabit Ethernet, ATM, and

FDDI.

PEDRIVER, the cluster port driver, provides cluster communications over LANs

using the NISCA protocol. Originally designed for broadcast media, PEDRIVER

has been redesigned to exploit all the advantages offered by switched LANs,

including full duplex transmission and more complex network topologies.

Users of LANs for their node-to-node cluster communication will derive the

following beneﬁts from the redesigned PEDRIVER:

• Removal of restrictions for using Fast Ethernet, Gigabit Ethernet, and ATM

as cluster interconnects

• Improved performance due to better path selection, multipath load

distribution, and support of full duplex communication

• Greater scalability

• Ability to monitor, manage, and display information needed to diagnose

problems with cluster use of LAN adapters and paths

4–10 System Management Features