In virtual storage environments, achieving optimal resource utilization, high throughput, and low response times is essential, as is preventing system overloads. Multipath I/O (MPIO) for iSCSI connections can enhance failover and load balancing capabilities, ensuring a more reliable and efficient storage service.

Synology NAS devices equipped with two or more network interfaces support MPIO for iSCSI Targets, enabling effective failover and load balancing arrangements. This article guides you through using iSCSI Targets on VMware ESXi Server with MPIO support.

• Synology NAS:
  • SAN Manager (or iSCSI Manager for older DSM versions):
    • iSCSI LUNs and Targets have been created.
    • Allow multiple sessions from one or more iSCSI initiators has been selected (configurable at SAN Manager > iSCSI > Edit > Advanced).

1. Launch vSphere Client and go to Configuration > Networking to click Add Networking.
   
2. Select VMKernel.
   
3. Create a new network switch and select a NIC located on another subnet.
4. Name the new network.
   
5. Select Obtain IP settings automatically.
   
6. Confirm all the settings and click Finish to complete the setup.
   
7. In Configuration > Storage Adapters, select the iSCSI Software Adapter and click Properties.
   
8. Make sure the iSCSI Initiator is Enabled. If not, click Configure… to enable it.
   
9. Once the iSCSI Initiator is enabled, go to Dynamic Discovery and click Add to enter the primary IP Address of the Synology NAS.
   
10. Rescan the Host Bus Adapter, and the iSCSI Initiator will detect the Target on the Synology NAS.
    
11. In Paths, right-click on the Target and click Manage Paths.
    
12. Select Round Robin (VMware). Note that, within the path management, the ESXi server is using two paths (via two subnets) to connect to the same iSCSI Target.