[T Series]A LUN Failure Led to a Failure to Initialize LUNs on the Host

Publication Date:  2012-07-19 Views:  95 Downloads:  0
Issue Description

Product and version information:

  • S5500T V100R001 V100R002
  • S5600T V100R001 V100R002
  • S5800T V100R001 V100R002
  • S6800T V100R001 V100R002
  • Application server operating system: Windows Server 2003 Enterprise X64 Edition

The UltraPath was installed on the host. The system had two disk enclosures, and mapped four LUNs to the host.
The expansion cables connecting controller A to the disk enclosures ware removed. The disks in the disk enclosures were in single-link mode. We viewed on the device management on the host that there were four physical disks and four virtual disks.
We ran the sys stopfd command on controller B in MML mode to restart controller B. At this time, a LUN in a disk enclosure failed.
After controller B reset, we saw in the device management on the host that four physical disks were displayed but no virtual disk. The output is shown in Figure1
Figure 1 Device management

Alarm Information
Handling Process

1. Delete manually the physical disks on the device manager
as shown in Figure2.

Figure 2 Device management


2. Refresh the device manager again. The system automatically generates physical disks and a corresponding virtual disk
as shown in Figure3.

Figure 3 Device management


Root Cause
Since the disk enclosures were connected to controller B through single links, the disk enclosures became offline when controller B was powered off. The system prioritized the handling of the controller power-off. The system was supposed to handle the disk enclosure offline after the controller power-off. However, because controller B was powered on at that time so the system prioritized the controller power-on. During the process, controller B set up a connection to the host, and the storage device reported the LUN to the host. When the LUN was being initialized, the system set the LUN to the invalid state. In such a situation, the LUN was not deleted, but was not available. Therefore, when the LUN recovered from the invalid state, the host could not create LUNs by scanning for disks. This resulted in the failure to initialize LUNs and generate virtual disks.
After the disk enclosures are powered off, Wait 30 seconds and then power them on.