The post will share a case for an I/O error is reported when LUNs from Active-Active arrays are mapped to RHEL 7.3 hosts and the Built-in multipath is used.
Problem Description
Two OceanStor 5300 V3 storage devices are deployed in active-active mode, and LUNs from both devices are mapped to RHEL 7.3 hosts who work as a cluster. In a dual-switch networking, both devices show that the LUNs run properly. The LUNs are displayed on one host but only local disks are displayed in the other host by running the fdisk -l command. An I/O error is reported and the mapped LUNs cannot be operated.
Handling Process
UltraPath of V1R8C50SCP200 does not support the operating system RHEL 7.3 and only multipath delivered with the operating system can be used.
1. Check that the LUNs are normal in both storage devices.
2. Check that initiators are online.
3. Check that the LUNs are mapped properly.
4. Check the HyperMetro pair. It is found that the LUNs at the primary end are in the read/write state, the LUNs at the secondary end cannot be accessed, and the HyperMetro pair is suspended.
5. Run the multipath -ll command on the host. It is found that half of the paths are failed. The secondary storage device may be faulty. Remove the mapping of the secondary storage device and restart the host. The LUNs mapped from the storage device can be identified.
Root Cause
The multipathing software that supports HyperMetro virtualizes all LUNs in a HyperMetro pair into one. However, the non-preferred site cannot access the LUN. As a result, an I/O error is reported when the command is executed.
Solution
Use the LUNs after HyperMetro pairs are synchronized.
Suggestions
You are advised to install Huawei UltraPath that supports RHEL 7.3.
