2.5 OpenVMS Galaxy Benefits
Many of the the benefits of OpenVMS Galaxy technol-
ogy result directly from running multiple instances of the
OpenVMS operating system in a single computer.
With several instances of OpenVMS in memory at the same
time, an OpenVMS Galaxy computing environment gives you
quantum improvements in:
* Compatibility-Existing applications run without changes.
* Availability-Presents opportunities to upgrade software
and expand system capacity without down time.
* Scalability-Offers scaling alternatives that improve per-
formance of SMP and cluster environments.
* Adaptability-Physical resources can be dynamically
reassigned to meet changing workload demands.
* Cost of ownership-Fewer computer systems reduce
system management requirements, floor space, and more.
The following descriptions provide more details about these
benefits.
Compatibility
Existing single-system applications will run without changes
on instances in an OpenVMS Galaxy. Existing OpenVMS
Cluster applications will also run without changes on clus-
tered instances in an OpenVMS Galaxy.
Availability
An OpenVMS Galaxy system is more available than a tra-
ditional, single-system-view, SMP system because multiple
instances of the operating system control hardware resources.
OpenVMS Galaxy allows you to run different versions of
OpenVMS (Version 7.2 and later) simultaneously. For exam-
ple, you can test a new version of the operating system or an
application in one instance while continuing to run the cur-
rent version the other instances. You can then upgrade your
entire system, one instance at a time.
Scalability
System managers can assign resources to match applica-
tion requirements as business needs grow or change. When a
CPU is added to a Galaxy configuration, it can be assigned to
any instance of OpenVMS. This means that applications can
realize 100 % of a CPU's power.
Typical SMP scaling issues do not restrict an OpenVMS
Galaxy. System managers can define the number of
OpenVMS instances, assign the number of CPUs in each
instance, and control how they are used.
Additionally, a trial-and-error method of evaluating re-
sources is a viable strategy. System managers can reassign
CPUs among instances of OpenVMS until the most ef-
fective combination of resources is found. All instances of
OpenVMS and their applications continue to run while CPUs
are reassigned.
Adaptability
An OpenVMS Galaxy is highly adaptable because computing
resources can be dynamically reassigned to other instances of
the operating system while all applications continue to run.
Reassigning CPUs best demonstrates the adaptive capability
of an OpenVMS Galaxy computing environment. For ex-
ample, if a system manager knows that resource demands
change at certain times, the system manager can write a
command procedure to reassign CPUs to other instances of
OpenVMS and submit the procdure to a batch queue. The
same could be done to manage system load characteristics.
In an OpenVMS Galaxy environment, software is in total
control of assigning and dynamically reassigning hardware
resources. As additional hardware is added to an OpenVMS
Galaxy system, resources can be added to existing instances;
or new instances can be defined without affecting running
applications.
Cost of ownership
An OpenVMS Galaxy presents opportunities to upgrade ex-
isting computers and expand their capacity, or to replace
some number of computers, whether they are cluster mem-
bers or independent systems, with a single computer running
multiple instances of the operating system. Fewer computers
greatly reduces system management requirements as well as
floor space.
Performance
An OpenVMS Galaxy can provide high commercial appli-
cation performance by eliminating many SMP and cluster-
scaling bottlenecks. Also, the distribution of interrupts across
instances provides many I/O configuration possibilities; for
example, a system's I/O workload can be partitioned so that
certain I/O traffic is done on specific instances.