Detection of response delay from the external storage system and actions to take

• Failure in the external storage system connected to the local storage system
• Failure on the communication path (including switches) between storage systems

When a command is issued from the local storage system to the external storage system, if the response from the external storage system is delayed for more than the I/O timeout value for the external path (15 seconds by default), a timeout occurs. In a configuration with duplicate external paths, the command is retried on the other external path, and the processing continues. However, if the timeout is caused by a failure in the external storage system or on the communication path (including switches), the timeout might continue to occur even after the active path is switched to the other external path. If you detect the cause (such as a failure in the external storage system or on the communication path) and take appropriate actions, the response delay between a host and the storage system might be resolved.

• If a timeout occurs more than a certain number of times within a certain period, SIM 21d2xx is reported.
• If you set system option mode (SOM) 1282 to ON, SIM 21d2xx is reported regardless of the I/O timeout value for the external path. In this case, SIM 21d2xx is reported even when a response delay (from the external storage system) longer than 15 seconds occurs more than a certain number of times. This function is supported by DKCMAIN microcode version 90-08-81-00/00 or later for VSP 5000 series and 93-06-81-x0/00 or later for VSP E series. To set SOM 1282 to ON, contact customer support.

• Various types of setting values set for the external storage system
• Excessive performance load on the external storage system
• Excessive performance load on the communication path

Check whether any of these problems occurs and, if necessary, take appropriate actions.