Running the Read Link Status Diagnostics

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Read Link Status error counts refer to link errors that have been detected in the traffic flow of a Fibre Channel loop. The errors detected are represented as a count (32 bit field) of error occurrences accumulated over time and help to provide a coarse measure of the integrity of the components and devices on the loop.

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The Read Link Status Diagnostics dialog retrieves the error counts and displays the controllers, drives, ESMs and Fibre Channel ports in channel order.

By analyzing the error counts retrieved, it is possible to determine the components or devices within the Fibre Channel loop which may be experiencing problems communicating with the other devices on the loop. A high error count for a particular component or device indicates that it may be experiencing problems, and should be given immediate attention.

Error counts are calculated from the current baseline , and may be reset by defining a new baseline. For more information, see How to Set the Baseline.

How to Run the Read Link Status Diagnostics

1

Select the storage subsystem from the Subsystem Management Window, then, select either the Storage Subsystem >> Run Read Link Status Diagnostics pull-down menu option, or Run Read Link Status Diagnostics from the right-mouse pop-up menu.

Result: The Read Link Status Diagnostics dialog is displayed, showing the error count data retrieved. The following data is displayed:

Devices

A list of all the devices on the Fibre Channel loop.

The devices are displayed in channel order, and within each channel they are sorted according to the devices position within the loop.

Baseline Time

The date and time of when the baseline was last set.

Elapsed Time

The elapsed time between when the Baseline Time was set, and when the read link status data was gathered using the Run option.

ITW

The total number of Invalid Transmission Word (ITW) errors detected on the Fibre Channel loop from the baseline time to the current date and time. ITW may also be referred to as the "Received Bad Character Count."

Tip: This is the key error count to be used when analyzing the error count data.

LF

The total number of Link Failure (LF) errors detected on the Fibre Channel loop from the baseline time to the current date and time.

LOS

The total number of Loss of Synchronization (LOS) errors detected on the Fibre Channel loop from the baseline time to the current date and time.

LOSG

The total number of Loss of Signal (LOSG) errors detected on the Fibre Channel loop from the baseline date to the current date and time.

PSP

The total number of Primitive Sequence Protocol (PSP) errors detected on the Fibre Channel loop from the baseline date to the current date and time.

ICRC

The total number of Invalid Cyclic Redundancy Check (ICRC) errors detected on the Fibre Channel loop, from the baseline date to the current date and time.

2

Interpret the results to determine where problematic components or devices are located. For more information, see How to Interpret Results.

How to Set the Baseline

Error counts are calculated from a baseline (which describes the error count values for each type of device in the Fibre Channel loop), from the time when the baseline was established to the time at which the error count information is requested.

The baseline is automatically set by the controller, however, a new baseline may be set manually through the Read Link Status Diagnostics dialog using the following steps:

Important: This option establishes new baseline error counts for ALL devices currently initialized on the loop.

1

Select Set Baseline.

Result: A confirmation dialog is displayed.

2

Select Yes to confirm baseline change.

Result: If the new baseline is successfully set, a success message is displayed indicating that the change has been made.

3

Select OK.

Result: The Read Link Status Diagnostics dialog is displayed.

4 Select Run to retrieve the current error counts.

How to Interpret Results

Analysis of the Read Link Status results is based on the principle that the device immediately 'downstream' of the problematic component should see the largest number of ITW error counts. The process involves obtaining the ITW count for every component and device on the loop, analyzing the data in loop order, and then identifying any large jumps in the ITW counts.

If you are unable to determine which component is problematic, save your results and forward them to technical support.

1

Open the Read Link Status Diagnostics dialog.

2

Look at the ITW column in the Read Link Status Diagnostics dialog and identify any unusual increase in the ITW counts.

Example

An increase in the ITW column of 10 to 40 counts over a 24 hour period indicates that there is possibly a component or device in the loop which is experiencing problems. Typically, the ITW count should not change by more than a few counts over this period of time.

Note: This is only an example and is not applicable to all situations.

Important: Because the current error counting standard is vague about when the ITW error count is calculated, different vendor's devices calculate at different rates. Analysis of the data must take this into account.

3

Select Close to return to the Subsystem Management Window, and troubleshoot the problematic devices. If you are unable to determine which component is problematic, save your results and forward them to technical support.

How to Save Diagnostics Results

For further troubleshooting assistance, save the Read Link Status results and forward them to technical support for assistance.

1

Select Save As.

Result: The Save As dialog is displayed.

2

Select a directory and type the file name of your choice in the File name text box. You do not need to specify a file extension.

3

Select Save.

Result: A comma-delimited file containing the read link status results is saved.

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