The S2600 Connects to a Switch by FC but the Switch Fails to Start Ater Luns are Mapped

Publication Date:  2012-07-22 Views:  142 Downloads:  0
Issue Description
An S2600 connects to an IBM3650 server by using a Brocade 200E switch. The IBM3650 runs the Linux AS4 operating system and can discover the 2 TB LUNs mapped from the S2600.
However, after some application programs are installed on the server, it fails to be restarted as required. An alarm is generated, indicating that the startup location is incorrect, and a floppy disk is required to boot the system.
Alarm Information
None
Handling Process
IBM engineers change the disk IDs in BIOS, and then the startup succeeds.  
Root Cause
If the optical fibers are removed before the server startup, its operating system is successfully booted. After the optical fibers are plugged to the server, it detects LUNs normally. However, if the server is started without removing optical fibers, its operating system fails to be booted. This is an unacceptable symptom for customers. With the help of IBM engineers, the reason is found out that the mapped LUNs occupy the IDs of the existing disks in the server, and then the operating system is booted from the mapped LUNs and the startup fails.
Suggestions
This failure occurs at a low probability, and it is closely related to the server, its HBA, and the HBA driver. According to further tests, this failure seldom occurs on servers of the same type. Furthermore, after the HBA on the server in this example is changed, the fault is rectified as well. In all, if the mentioned failure occurs, change the HBA or disk IDs to rectify it.

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