## Configuration Types and Diagnostic Examples

##

## Configurations

## Type 1

## Type 2

## Additional configurations

## Diagnostic Examples

##

## Type 1 configuration

The identifying features of a type 1 configuration (as shown in Figure 1) are:

- Host adapters are connected directly to one port of Controller A and B, with one or more host adapters per system.
- Multiple servers can be connected, but without system-to-system failover (no MSCS).
- In a dual controller environment, limited redundancy can be achieved by adding an HBA to each of the servers. This will provide path and HBA redundancy.
- Uses some type of isolation mechanism (such as partitions) between server resources.

Figure 1. Type 1 configuration

Dual Controller

Single Controller

## Type 2 configuration

The type 2 configuration can occur with or without switches, as shown in Figure 2 and Figure 3.

Figure 2. Type 2 configuration - With switches.

The identifying features of a type 2 configuration are:

- Multiple host adapters are connected for full redundancy across systems having failover support such as MSCS.
- Host adapters are connected either directly to ports or through switches (2 SFP ports per controllers).

Figure 3. Type 2 configuration - Without switches

## Diagnostics and examples

In a type 1 configuration there are no externally managed switches to aid in debugging. The diagnostic tools available are the HBA Loopback test, FAStT MSJ (from the host adapter end) and the Controller Loopback test (from the RAID controller end). If you intend to diagnose a failed path while using the alternate path for production, be sure that you are familiar with the tools and the loop connections so that the correct portion is being exercised and you do not unplug anything in the active path.

For a type 2 configuration, use the features of the switches and the capability of MSCS to isolate resources from the bad or marginal path before beginning debug activities. Switches allow a view of log information that shows what problems have been occurring, as well as diagnostics that can be initiated from these managed elements. Also, a type 2 configuration has the capability to have more than one RAID controller unit behind a switch. In the diagnostic maps, the switches are referred to generically as concentrators. Figure 4 shows a type 2 configuration with multiple controller units.

Figure 4. Type 2 configuration with multiple controller units

### Debugging example sequence

An example sequence for debugging a type 2 MSCS configuration is shown in the following sequence of figures.

You can attach multiple server pairs to the switches by using zoning or partitioning for pair isolation or combinations of type 1 and type 2 configurations. Break the larger configuration into its smaller sub elements and work with each piece separately. In this way you can remove the good path and leave only the bad path, as shown in the following sequence.

1. One controller is off-line. In the example shown in Figure 5, controller B is off-line.

Figure 5. Offline controller B

2. All I/O is flowing through controller A. Controller B is now off-line and can be debugged. This yields the diagram shown in Figure 6 for debugging.

Figure 6. All I/O flowing through controller A

Controller A is processing I/Os and is unavailable for diagnostics

3. To see more clearly what is involved, redraw the configuration showing the path elements in the loop, as shown in Figure 7.

Figure 7. Path elements loop

The elements of the paths shown in Figure 7 are as follows:

1. Host adapter with optical transceiver

Note: Some HBAs do not have integrated transceivers and therefore require an SFP.

2. Optical transceiver in switch (SFP)
3. SFP in controller port
4. RAID controller
5. Optical cables

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