NonStop NS-Series Planning Guide (H06.03+)

Introduction to Integrity NonStop NS-Series Systems
HP Integrity NonStop NS-Series Planning Guide—529567-004
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Failure Recovery for Triplex Processor
Failure Recovery for Triplex Processor
In triplex processors, each LSU has inputs from the three processor elements within a
logical processor. As with the duplex processor, the LSU keeps the three PEs in loose
lockstep. The LSU also checks the outputs from the three PEs. If outputs from one of
the PEs is not the same as the other two, the errant result is ignored, and the result
from the other two PEs is sent to the ServerNet fabrics. Reintegration works the same
as in the duplex processor. The number of PEs in a reintegration depends on the
conditions of the failure and the configuration of the hardware.
The failure of a slice in a triplex processor reduces processor operation to duplex.
When the failing unit is replaced, the reintegration function restores the system to
triplex operation. If failure of an LSU takes down its associated logical processor, the
operating system activates the backup processes in other logical processors. The
system runs user applications as if no failure occurred.
As with a duplex processor, the errant processor is reset and then it is synchronized
with the running processors. Should the failure rate exceed a predetermined threshold
value within a period of time, the failing processor is reset and held for repair action.
ServerNet Fabric I/O
The ServerNet fabric used in Integrity NonStop NS-series is ServerNet 3, which uses
fiber-optic links exclusively and is a collection of connected routers and links that form
a flexible internal or external network. For details of the ServerNet fabric, see
Section 3, ServerNet Communications Network.
Two separate, identically configured fabrics, called the X fabric and the Y fabric,
together provide a fault-tolerant interconnection for the ServerNet network via