Technical data
System Management Features
4.9 OpenVMS Cluster Systems
4.9.2 Fast Path for SCSI and Fibre Channel (Alpha)
Fast Path for SCSI and Fibre Channel (FC) is a new feature with OpenVMS
Version 7.3. This feature improves the performance of Symmetric Multi-
Processing (SMP) machines that use certain SCSI ports, or FC.
In previous versions of OpenVMS, SCSI and FC I/O completion was processed
solely by the primary CPU. When Fast Path is enabled, the I/O completion
processing can occur on all the processors in the SMP system. This substantially
increases the potential I/O throughput on an SMP system, and helps to prevent
the primary CPU from becoming saturated.
See Section 4.12.2 for information about the SYSGEN parameter, FAST_PATH_
PORTS, that has been introduced to control Fast Path for SCSI and FC.
4.9.3 Floppy Disks Served in an OpenVMS Cluster System (Alpha)
Until this release, MSCP was limited to serving disks. Beginning with OpenVMS
Version 7.3, serving floppy disks in an OpenVMS Cluster system is supported,
enabled by MSCP.
For floppy disks to be served in an OpenVMS Cluster system, floppy disk names
must conform to the naming conventions for port allocation class names. For
more information about device naming with port allocation classes, refer to the
OpenVMS Cluster Systems manual.
OpenVMS VAX clients can access floppy disks served from OpenVMS Alpha
Version 7.3 MSCP servers, but OpenVMS VAX systems cannot serve floppy disks.
Client systems can be any version that supports port allocation classes.
4.9.4 New Fibre Channel Support (Alpha)
Support for new Fibre Channel hardware, larger configurations, Fibre Channel
Fast Path, and larger I/O operations is included in OpenVMS Version 7.3. The
benefits include:
• Support for a broader range of configurations: the lower cost HSG60
controller supports two SCSI buses instead of six SCSI buses supported
by the HSG80; multiple DSGGB 16-port Fibre Channel switches enable very
large configurations.
• Backup operations to tape, enabled by the new Modular Data Router (MDR),
using existing SCSI tape subsystems
• Distances up to 100 kilometers between systems, enabling more configuration
choices for multiple-site OpenVMS Cluster systems
• Better performance for certain types of I/O due to Fibre Channel Fast Path
and support for larger I/O requests
The following new Fibre Channel hardware has been qualified on OpenVMS
Version 7.2-1 and on OpenVMS Version 7.3:
• KGPSA-CA host adapter
• DSGGB-AA switch (8 ports) and DSGGB-AB switch (16 ports)
• HSG60 storage controller (MA6000 storage subsystem)
• Compaq Modular Data Router (MDR)
OpenVMS now supports Fibre Channel fabrics. A Fibre Channel fabric is
multiple Fibre Channel switches connected together. (A Fibre Channel fabric is
also known as cascaded switches.)
System Management Features 4–9