Silicon Graphics InfiniteStorage 4000 Series, Настройка и обслуживание

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Chapter 11: Maintaining a Storage Array 197
Interpreting the RLS Results
The way that you interpret the RLS results is based on the concept that the device
immediately following the problematic component will have the largest number of
invalid transition word (ITW) error counts. The process is to obtain the ITW count for
every component and device on the loop, analyze the data in loop order, and identify
any large increases in the ITW counts.
NOTE
The current error counting standard for when to calculate the ITW error count
is not well defined. Different vendor devices calculate at different rates. Analysis of the
data must take this discrepancy into consideration.
Collecting
Switch-on-a-Chip
Error Statistics
Switch-on-a-chip (SOC) error statistics provide information about the loop-switch
ports that are connected to the Fibre Channel devices in a storage array. (RLS counts
provide information about the Fibre Channel devices.) Reporting SOC error statistics
is available only on storage arrays that have SOC loop-switch devices that are
incorporated into the controller drive channel or the ESM circuitry. SOC devices are
integrated circuits that join together Fibre Channel devices in arbitrated loop
topologies. SOC devices automatically collect statistical information for each SOC
port that is connected to a controller port, an ESM port, a drive port, or an expansion
connector. Your Technical Support representative can use the statistical information
with RLS counts to identify problems with Fibre Channel devices that are attached to
the loop.
SOC error statics include this information:

The port state

The port insertion count

The loop state

The loop up count

The CRC error count

The relative frequency drift error average
Invalid cyclic redundancy
check (ICRC)
The total number of ICRC errors that were detected on the Fibre
Channel loop from the baseline date to the current date and time.
An ICRC count indicates that a frame has been received with an invalid
cyclic redundancy check value. A cyclic redundancy check reads the
data, calculates the cyclic redundancy check character, and compares
the calculated cyclic redundancy check character with a cyclic check
character already present in the data. If they are equal, the new data is
presumed to be the same as the old data. If the calculated characters
and the old characters do not match, an error is posted, and the data is
re-sent.
Type of Data Description