An OpenVMS Galaxy computing environment lets customers decide
how much cooperation exists between instances in a single computer
system.
In a shared-nothing computing
model, the instances do not share any resources; operations are
isolated from one another (see the Section
Shared-Nothing Computing Model).
In a shared-partial computing
model, the instances share some resources and cooperate in a limited
way (see the Section
Shared-Partial Computing Model).
In a shared-everything model,
the instances cooperate fully and share all available resources,
to the point where the operating system presents a single cohesive
entity to the network (see the Section
Shared-Everything Computing Model).
Shared-Nothing Computing
Model In
a shared-nothing configuration (shown in
Shared-Nothing Computing Model), the instances of OpenVMS are completely independent
of each other and are connected through external interconnects,
as though they were separate computers.
With Galaxy, all available memory is allocated into private
memory for each instance of OpenVMS. Each instance has its own set
of CPUs and an appropriate amount of I/O resources assigned to it.
Figure 3 Shared-Nothing
Computing Model
Shared-Partial Computing
Model In
a shared-partial configuration (shown in
Shared-Partial Computing Model), a portion of system memory is designated as shared memory,
which each instance can access. Code and data for each instance
are contained in private memory. Data that is shared by applications
in several instances is stored in shared memory.
The instances are not clustered.
Figure 4 Shared-Partial
Computing Model
Shared-Everything
Computing Model In
a shared-everything configuration (shown in
Shared-Everything Computing Model), the instances share memory and are clustered with
one another.