PEX 8717, PCI Express Gen 3 Switch, 16 Lanes, 10 Ports

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8/1/2011, Version 1.0

Error Injection & SerDes Loopback

Using the PEX 8717’s Error Injection feature, users can

inject malformed packets and/or fatal errors into their

system and evaluate a system’s ability to detect and

recover from such errors. The PEX 8717 also supports

Internal Tx, External Tx, Recovered Clock, and Recovered

Data Loopback modes.

Applications

Suitable for host-centric as well as peer-to-peer traffic

patterns, the PEX 8717 can be configured for a wide

variety of form factors and applications.

Host Centric Fan-out

The PEX 8717, with its symmetric or asymmetric lane

configuration capability, allows user-specific tuning to a

variety of host-centric applications. Figure 6 shows a

server design where, in a quad or multi processor system,

users can assign endpoints/slots to CPU cores to distribute

the system load. The packets directed to different CPU

cores will go to different (user assigned) PEX 8717

upstream ports, allowing better queuing and load balancing

capability for

higher

performance.

Conversely, the

PEX 8717 can

also be used in

single-host

mode to simply

fan-out to

endpoints.

Figure 6. Host Centric Dual Upstream

Multi-Host Systems

In multi-host mode, the PEX 8717 can be shared by up to

two hosts in a

system. By creating

two virtual switches,

the PEX 8717

allows two hosts to

fan-out to their

respective

endpoints. This

reduces the number

Figure 7. Multi-Host System

of switches required for fan-out, saving precious board

space and power consumption. In Figure 7, the PEX 8717

is being shared by two different servers (hosts)

with each server is running its own applications (I/Os).

The PEX 8717 assigns the endpoints to the appropriate

host and isolates them from the other hosts.

Host Failover

The PEX 8717 can also be utilized in applications where

host failover is required. In the below application (Figure

8), two hosts may be active simultaneously and controlling

their own domains while exchange status information

through doorbell registers or I

be programmed to trigger fail-over if the heartbeat

information is not provided. In the event of a failure, the

surviving device

will reset the

endpoints

connected to the

failing CPU and

enumerate them in

its own domain

without impacting

the operation of

endpoints already

in its domain.

Figure 8. Host Fail-Over

N+1 Fail-Over in Storage Systems

The PEX 8717’s Multi-Host feature can also be used to

develop storage array clusters where each host manages a

set of storage devices independent of others (Figure 9).

Users can designate one of the hosts as the failover-host

for all the other hosts while actively managing its own

endpoints. The failover-host will communicate with other

hosts for status/heartbeat information and execute a

failover event if/when it gets triggered.

Figure 9. N+1 Failover