10.3 Common issues 10.3.1 Host problems GLYPH<SM590000> lshost SANs, storage subsystems and host systems can be complicated. They often consist of  hundreds or thousands of disks, multiple redundant subsystem controllers, virtualization  engines, and different types of SAN switches. All of these components must be configured,  monitored, and managed properly. If issues occur, administrators must know what to look for  and where to look. IBM FlashSystem 9100 has useful error logging mechanisms. It keeps track of its internal  events and informs the user about issues in the SAN or storage subsystem. It also helps to  isolate problems with the attached host systems. So, with these functions, administrators can  easily locate any issue areas and take the necessary steps to fix any events.  In many cases, IBM FlashSystem 9100 and its service and maintenance features guide  administrators directly, provide help, and suggest remedial action. Furthermore, IBM  FlashSystem 9100 determines whether the problem still persists or not. Another feature that helps administrators to isolate and identify issues that might be related to  IBM FlashSystem 9100 is the ability of their nodes to maintain a database of other devices  that communicate with the IBM FlashSystem 9100 device. Devices, like hosts and optional  back-end storages, are added or removed from the database as they start or stop  communicating to IBM FlashSystem 9100. Although IBM FlashSystem 9100 node hardware and software events can be verified in the  GUI or CLI, external events like failures in the SAN zoning configuration, hosts, and back-end  storages are common. They need to have a troubleshooting performed outside of IBM  FlashSystem 9100, too. As an example, a misconfiguration in the SAN zoning might lead to  the IBM FlashSystem 9100 cluster not working properly. This problem occurs because the  IBM FlashSystem 9100 cluster nodes communicate with each other by using the Fibre  Channel SAN fabrics. In this case, check the following areas from an IBM FlashSystem 9100 perspective: From the host perspective, you can experience various situations that range from  performance degradation to inaccessible disks. To diagnose any host-related issue, you can  start checking the hosts configuration on IBM FlashSystem 9100 side. The  Hosts  panel in the  GUI or the following CLI commands should be used to start a verification in any possible  hosts related issue: Check the host’s status. If status is  online , the host ports are online in both nodes of an  I/O group. If status is  offline , the host ports are offline in both nodes of an I/O group. If  status is  inactive , it means that the host has volumes mapped to it, but all of its ports  have no SCSI commands in the last 5 minutes. Also, if status is  degraded , it means at least  one but not all of the host ports is not online in at least one node of an I/O group.  GLYPH<SM590000> The attached hosts. For more information, see 10.3.1, “Host problems” on page 362. GLYPH<SM590000> The SAN. For more information, see 10.3.2, “SAN events” on page 364. GLYPH<SM590000> The optional attached storage subsystem. For more information, see 10.3.3, “Storage  subsystem issues” on page 364. GLYPH<SM590000> The local FC port masking. For more information, see 10.3.4, “Port masking issues” on  page 369. 362  IBM FlashSystem 9200 and 9100 Best Practices and Performance Guidelines