Read link status error counts refer to link errors that have been detected in the traffic flow of a loop. The errors detected are represented as a count (32-bit field) of error occurrences accumulated over time. The errors
provide a coarse measurement of the integrity of the components and on the loop.
Important:
Use this option only under the guidance of a representative.
The Read Link Status Diagnostics dialog retrieves the error counts and shows the , disk drives, and Fibre Channel ports in channel order.
By analyzing the error counts retrieved, you can determine the components or storage subsystems within the Fibre Channel loop
that might be experiencing problems communicating with the other storage subsystems on the loop. A high error count for a
particular component or storage subsystem indicates that it might be experiencing problems and should be given immediate attention.
Error counts are calculated from the current and might be reset by defining a new baseline. For more information, see step 3.
Select one of these tasks, and go to the indicated step:
To run the read link diagnostics, perform these substeps:
From the Subsystem Management Window, select a storage subsystem, and select Advanced >> Troubleshooting >> Run Diagnostics >> Read Link Status.This information appears:
Devices – A list of all of the storage subsystems on the Fibre Channel loop. The storage subsystems appear in channel order, and
within each channel they are sorted according to thestorage subsystem’s position within the loop.
Controller/Port – The controller ID or the ID of the device.
ALPA ID – The of the device.
Baseline Time – The date and time of when the baseline was last set.
Sampling Interval – 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 errors detected on the Fibre Channel loop from the baseline time to the current date and time. ITW might be referred to as
the “Received Bad Character Count.” ITW is the key error count to be used when analyzing the error count data.
LF – The total number of errors detected on the Fibre Channel loop from the baseline time to the current date and time.
LOS – The total number of errors detected on the Fibre Channel loop from the baseline time to the current date and time.
LOSG – The total number of errors detected on the Fibre Channel loop from the baseline time 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 time
to the current date and time.
ICRC – The total number of errors detected on the Fibre Channel loop from the baseline time to the current date and time.
To view error count data for a particular device, select the device from the Show devices on list.
Interpret the results to determine where problematic components or storage subsystems are located. For more information, see
step 4. You are finished with this procedure.
To set the baseline, you need to understand some concepts about baselines.
Error counts are calculated from a baseline (which describes the error count values for each type of storage subsystem 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. You can also manually set a new baseline through the Read Link Status Diagnostics dialog.
Important:
This option establishes new baseline error counts for all storage subsystems currently on the loop.
To set the baseline, perform these substeps:
Select Set Baseline.
Click Yes.
Click OK.
To retrieve the current error counts, click Run. You are finished with this procedure.
To interpret the results, you need to understand some concepts about the results you will receive:
Analysis of the read link status results is based on the principle that the storage subsystem immediately “downstream” of
the problematic component should see the largest number of invalid transmission word (ITW) error counts. The process involves
these tasks:
Obtaining the ITW count for every component and storage subsystem on the loop
Analyzing the data in loop order
identifying any large jumps in the ITW counts
For example, an increase in the ITW column of 10 to 40 counts over a 24-hour period indicates that a component or storage
subsystem in the loop is experiencing problems. Typically, the ITW count should not change by more than a few counts over
this period of time.
Important:
Because the current error counting standard is vague about when the ITW error count is calculated, different vendor's storage
subsystems calculate at different rates. When you analyze the data, take this concept into account.
Note:
When you analyze read link status (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. The NA indicates that
the SATA disk drives are not communicating with the controller through the Fibre Channel (FC) protocol. However, if there
are any SATA drive expansion enclosures in the storage subsystem, the ESMs in those drive expansion enclosures are identified
as Fibre Channel devices. Therefore, they report meaningful RLS data back to the controller. The SATA disk drives behind the
ESMs report RLS data, but this data is coming from the Fibre-to-SATA translation circuitry in the ESM.
To interpret the results, perform these substeps:
Open the Read Link Status Diagnostics dialog.
Look at the ITW column, and identify any unusual increase in the ITW counts. If you are unable to determine which component
is problematic, save your results, and forward them to a representative.
Click Close. You are finished with this procedure.
To save the diagnostic results, perform these substeps:
Note:
For further troubleshooting assistance, save the read link status results, and forward them to a representative for assistance.
Click Save As.
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.
Click Save.
A comma-delimited file containing the read link status results is saved. You are finished with this procedure.