Hard Disks are in the Single-link State Randomly Due to the Incorrect Use of the Expansion Port

Publication Date:  2012-07-20 Views:  126 Downloads:  0
Issue Description
A customer uses an S5600 storage system that contains one controller enclosure and five disk enclosures. During the deployment, after the controller enclosure is connected to five disk enclosures by using port EXP0, the OSM is logged in to from the IE browser. On the device panel, part of hard disks distributed in different enclosures are in the single-link state (the background color of these disks is yellow).
Alarm Information
Handling Process

Step 1 Check the status of the two controllers on the OSM. They are in the normal state.


Step 2 Restart the S5600. The fault persists, but the slots and the number of the “yellow disks” are different from previous situation. Restart the S5600 twice again and find that the slots and the number of the “yellow disks” are different each time the S5600 is restarted. Therefore, these “yellow disks” appear randomly and are unrelated to the controllers.


Step 3 Consult the R&D engineers. The fault is caused by FC link limitation. Check the connection of optical fibers and find that the both controllers are connected to disk enclosure by using port EXP0. Reconnect the two controllers to disk enclosure by using port EXP1, and restart the S5600. The status of all disks become normal.

Root Cause
Only the disks that are in the normal physical state but identified by a single controller are displayed yellow in background color. These disks are in the single-link state.
An FC link supports a maximum of 127 nodes. For an S5000 storage system with 24 disk slots in an enclosure, an FC link supports a maximum of five enclosures. The link of port EXP0 includes the controller enclosure itself; therefore, port EXP0 supports a maximum of four disk enclosures. Port EXP1 supports a maximum of five disk enclosures.