Use the following settings on the external system:
- Set the ALUA mode to Enable because VSSB supports ALUA connection only. When the VSSB volumes are mapped, the ALUA mode is enabled by default. If you disable the ALUA mode, I/O performance might be degraded because I/O is issued on external paths that use VSSB ports with Active/Non-Optimized status.
- Set the number of VSSB nodes (physical servers) to no more than 8 and assign external paths equally to individual VSSB nodes.
For each LU in VSSB, the port status of one node is set to Active/Optimize, and the port status of other nodes is set to Active/Non-Optimize. On the other hand, the maximum number of external paths for the local storage system is 8 per LU. Therefore, if the number of VSSB nodes is 9 or more, the port status might be set to Non-Optimized for all external paths. As the result, when the number of VSSB nodes is 9 or more, I/O is issued on external paths that use VSSB ports with Active/Non-Optimized status, which might degrade I/O performance.