In virtual storage setups, ensuring optimal resource utilization, maximum throughput, minimized response times, and preventing overloads is crucial. Leveraging Multipath I/O (MPIO) for iSCSI connections enhances failover and load balancing capabilities, providing a superior, dependable storage service.

Widely supported by various technologies such as disk controllers, iSCSI protocol, Fibre Channel, and software from Linux, VMware, Microsoft, and others, MPIO offers better compatibility than Multiple Connection per Session (MC/S). 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 the process of using iSCSI Targets on Windows computers that accommodate MPIO.

Windows computer

• Windows Server 2022 has been installed.

Synology NAS

• SAN Manager:
  • 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 Server Manager and go to Dashboard > Manage > Add Features Wizard.
2. Select Multipath I/O and click Install.
   
3. After installation, restart your computer to apply all the modifications.
4. Go to Control Panel > MPIO > Discover Multi-Paths. Select Add support for iSCSI devices and click Add.
   
5. Restart your computer again, and a new device called "MSFT2005iSCSIBusType 0x9" (or similar ID) should appear in MPIO Properties > MPIO Devices.
   
6. Press Windows key + S and type iSCSI Initiator to launch iSCSI Initiator. Go to the Discovery tab and click Discover Portal… to add every IP address used by your Synology NAS. The IP addresses will appear in Target portals.
7. Go to the Targets tab, select a Target, and then click Connect.
8. Select Enable multi-path and click Advanced… to proceed.
9. Select Microsoft iSCSI Initiator from the Local Adapter drop-down list. Select an IP address from each of Initiator IP and Target portal IP drop-down lists. These two IP addresses must be in the same subnet.
10. Select a Target and click Properties… to enable MPIO.
11. Click Add session in the Sessions tab to add another path.
12. Select Enable multi-path and click Advanced… to proceed.
13. Select Microsoft iSCSI Initiator from the Local Adapter drop-down list. Select an IP address from the Initiator IP drop-down list, and then select another IP address other than the one specified in step 9 from the Target portal IP drop-down list. These two IP addresses must be in the same subnet.
    
14. On your Synology NAS, go to SAN Manager (or iSCSI Manager before DSM 7.0) to check if the two IP addresses are included in the Service Status.
15. Press Windows key + X and click Computer Management.. Go to Disk Management and right-click on your iSCSI disk (not partition or volume) to open the Properties window.
16. Go to the MPIO tab, and you will see both paths listed. You can choose a preferred MPIO policy here.