Learn About the Read Link Status Diagnostics

A loop is an interconnection used to connect components and storage subsystems. The storage management software uses the connection between the machine and each in the storage subsystem to communicate with each component and storage subsystem on the loop.

During communication between storage subsystems, are detected within the traffic flow of the loop. Error count information is accumulated over a period of time for each component and storage subsystem, including these components:

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

The controller automatically sets the baseline. However, you may use the Read Link Status Diagnostics dialog to set a new baseline manually. For more information, refer to the Running the Read Link Status Diagnostics online help topic.

Read Link Status Results

Analysis of the RLS error count data is based on the principle that the storage subsystem immediately “downstream” of the problematic component should see the largest number of error counts.


Important:

Because the current error counting standard is vague about when the ITW count is calculated, different vendors' storage subsystems calculate errors at different rates. Analysis of the data must take this into account.

The analysis process involves the following steps.

  1. Obtain an ITW error count for each component and storage subsystem on the loop.
  2. View the data in loop order.
  3. Identify any large increase in the ITW error counts.

In addition to the ITW count, these error counts are shown in the Read Link Status Diagnostics dialog.

Error count type and description

Error Count Type Definition of Error

Link Failure (LF)

When detected, indicate that a failure occurred within the laser operation of the media module.

Link failures also might be caused by a link fault signal, a loss of signal, or a loss of synchronization.

Loss of Synchronization (LOS)

An LOS indicates that the receiver cannot acquire symbol lock with the incoming data stream, due to a degraded input signal.

If this condition persists, the number of Loss of Signal errors increases.

Loss of Signal (LOSG)

An LOSG indicates a loss of signal from the transmitting node or physical component within the Fibre Channel loop.

Physical components where a loss of signal typically occurs include the gigabit interface converters, and the Fibre Channel fiber-optic cable.

Refers to the number of N_Port (Node Port) protocol errors detected, and Link Reset Response (LRR) primitive sequences received while the link is up.

A PSP refers to the number of protocol errors detected, and Link Reset Response (LRR) primitive sequences received while the link is up.

A Link Reset Response (LRR) is issued by another N_Port in response to a link reset.

Invalid Cyclic Redundancy Check (ICRC)

An ICRC indicates that a frame has been received with an value.

A cyclic redundancy check is performed by first reading the data. Then, the value of the cyclic redundancy check character is calculated. Finally, the calculated value is compared to the value of the cyclic check character already present in the data. If the values are equal, the new data is presumed to be the same as the old data.


Note:

When you analyze RLS data for a storage subsystem that contains both SATA disk drives and a controller in a single enclosure, you will see NA (Not Applicable) for each SATA disk drive in this enclosure. This condition is the result of the SATA disk drives not using the Fibre Channel (FC) protocol to communicate with the controller. However, if any SATA expansion drive expansion enclosures are in the storage subsystem, the ESMs in those enclosures are identified as Fibre Channel devices and will report meaningful RLS data back to the controller. The SATA disk drives behind the ESMs will report RLS data, but this data will be coming from the Fibre-to-SATA translation circuitry in the ESM.

If you are unable to determine which component or storage subsystem on your Fibre Channel loop is experiencing problems, save the RLS diagnostics results, and forward them to a representative for assistance.

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