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Knowledge Base

A problem caused by the arbitrated loop

Publication Date:  2012-11-24  |   Views:  79  |   Downloads:  0  |   Author:  c00230043  |   Document ID:  EKB1000020129

Contents

Issue Description

There is a set of S2600 in a certain site, mount the assigned LUN to the AIX midrange computer, and then create the VG and LV through the AIX midrange computer; and create a 1GB file system, the process of creating the VG is very slow, which persists more than 1 minute, meanwhile, create the LV very slowly, while creating the “jfs2log” file system and some other files, several minutes later, it is failed.
Retry for several times, and the problem is still on;
Because original LUN has been divided as 5.7T and mounted to the server directly, divide the LUN as 200GB, but the problem is still on;
Check the fiber cable link, it’s normal, and the FC switch distributes the Zone correctly.
We guess the multi-path software version isn’t compatible, unload the multi-path software from the host, and then retry, but the problem is still on.

Alarm Information

None

Handling Process

In the FC switch, view the storage and the host’s switch ports’ status, we find the status of the port connected with the storage’s host is L-port (Loop mode).
Login via the management software, check the host port port’s configuration, we find the storage’s FC host port is “arbitrated loop” by default, and it should be modified as to the “switch” mode.

Root Cause

From the symptom of the host, we hardly find the cause of the problem, the possible reason may be in the network layer or the host operating system, and it’s rather hard to locate it to the storage’s configuration.

Suggestions

In the condition that the storage connecting with the server directly, the host port’s mode is the default “arbitrated loop”, and in the condition that using the switch to connect, this configuration is “switch” mode. In the actual scene, we use the “switch” mode much more.
In addition, while there appears the configuration error, it’s hard to locate, so it’s not considered comprehensively for the maintenance availability while planning the software, and it needs o advanced.