NonStop Systems Introduction for H-Series RVUs

Integrity NonStop NS-Series Server Architecture
NonStop Systems Introduction for H-Series RVUs—540083-001
7-2
Software and Hardware Views of Architecture
called NonStop Blade Elements in the NonStop advanced architecture. Each
NonStop Blade Element houses two or four microprocessors called processor
elements. A logical processor consists of one processor element from each NonStop
Blade Element. Although a logical processor physically consists of multiple processor
elements, with each element contained in a separate enclosure, it is convenient to
think of a logical processor as a single entity within the system. Each logical processor
has its own memory and its own copy of the operating system and processes a single
instruction stream. Logical processors are usually referred to simply as “processors.”
A NonStop Blade Complex consisting of three NonStop Blade Elements, as shown in
Figure 7-2, is referred to as a triplex, or triple modular redundancy (TMR), system. A
duplex, or double modular redundancy, configuration (two NonStop Blade Elements) is
also available. In a duplex or triplex configuration, the system can continue to function
in the event of failure of a processor element. The failed component within a NonStop
Blade Element, such as a processor element, power supply, and so forth can be
replaced while the system continues to run. This approach provides fault tolerance not
found in traditional architectures.
As you might expect, the triplex system provides additional fault tolerance over the
duplex system. If a NonStop Blade Element should fail in a triplex system, one of the
two remaining functional NonStop Blade Elements takes over; the system becomes, in
effect, a duplex system, with one NonStop Blade Element remaining as a backup.
A single NonStop NS-series system can have up to four NonStop Blade Complexes for
a total of 16 processors. The system shown in Figure 7-2 on page 7-3 has one
NonStop Blade Complex with four processors. Processors communicate with each
other over dual ServerNet fabrics.