ServerNet Cluster Manual

ServerNet Cluster Description
ServerNet Cluster Manual—520575-003
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X and Y Fabrics
Expand Node Number
An Expand node number, sometimes called a “system number,” is a number that
identifies a system in an Expand network. A ServerNet node has both a ServerNet
node number and an Expand node number.
X and Y Fabrics
A collection of connected routers and ServerNet links is called a fabric. Two identically
configured fabrics, referred to as the X fabric and the Y fabric, together provide a fault-
tolerant interconnection for the server. Communication occurs on both fabrics
simultaneously for increased throughput.
Each processor connects to both fabrics. The X fabric and the Y fabric are not
connected to each other; therefore, a ServerNet packet cannot cross from one fabric to
the other, and a failure in one fabric does not affect the other fabric. This fault tolerance
at the hardware level enhances availability.
Internal ServerNet Fabrics
An internal ServerNet X or Y fabric delivers ServerNet packets between ServerNet end
devices within a server. The internal ServerNet X and Y fabrics are identical. ServerNet
messages are routed across the internal fabrics using server hardware such as
ServerNet Expansion Boards (SEBs) and Modular ServerNet Expansion Boards
(MSEBs).
Figure 1-8 shows a simplified logical diagram of the internal ServerNet X and Y fabrics.