Topology Test - Compaq ServerNet ServerNet II Installation Manual

H-6 Compaq ServerNet II PCI Adapter and Switch Installation Guide
Figure H-6. SPAD Driver Between SANMan and the SAN
If the echo test passes, but your application is unable to communicate between the nodes, it is
the upper-level protocol software (see Figure H-6) that is most likely at fault. This software is
not covered by the echo test. This software is positioned between your application and the
SPAD2 driver.
If echo tests pass to both target nodes "A" and "B", it means that your local host application
should have no problems communicating with services or other application components running
in those nodes. An echo test must be run on node "A" or "B" in order to verify that those two
nodes can communicate with each other. To thoroughly test your entire SAN, we recommend
that you run echo tests from all the nodes connected to the SAN. This requires installing
Diagnostics on all the nodes and running the tests from each node separately.

Topology Test

The topology test compares the expected with the actual topology of the SAN. The topology
includes the identity of the SAN nodes and how those nodes are connected to each other.
The expected topology is retrieved from the SANMan driver in the form of a Resident Topology
Description (RTD). The RTD is parsed to extract the needed information.
Probing the SAN with IBC requests discovers the actual topology. The identity of any working
SAN node can be obtained from that node using an IBC Read operation to obtain that node's
IBC Information Block. The IBC Information Block contains, among other things, the GUID of
the node, and how many ports the node has. (Ports are always numbered sequentially starting
with zero.) The test obtains this information from the (zero, or one, or two) nodes that are
directly connected to the local-host computer. The same information is then requested from
whatever node is connected to each port of the just discovered nodes. (Remember that a node
tells me what ports it has.) This probing progresses through the SAN until all discovered nodes
have had all their ports probed.
There is a slight variation when a switch node is discovered. Switch nodes can report the state of
their ports. When a switch node is discovered the port states are requested. Only those ports of
the switch that are in an 'alive' state are probed. This prevents the timeout delay of attempting
to probe disconnected Switch ports.
ServerNet
Network
Remote Node Computer
(aka: Target Node)
SANMAN
Adapter
Echo Test
Card
Response
Echo Test
Request
Your Application
Upper
Level
Protocol
Software
SPAD