iSCSI MPIO configuration in a HA cluster?

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iSCSI MPIO configuration in a HA cluster?

Unread post by jsingh » Mon Oct 17, 2016 8:32 am

We are currently testing SHA between two RS3614XS devices before we move into production. We have LAN1 to LAN4 configured with static IP individually on same subnet. LAN5 (10Gbps SFP+ card) is our heartbeat. Our issue is that we can't get iSCSI MPIO to work properly between our ESXi hosts and Synology once the SHA is enabled. I know that once the cluster is established, we have to stick with using just the single cluster IP address for everything and not touch other IPs. But the problem is, the way I understand is that the cluster IP address is attached to a single LAN port for the data network connection (this was selected during the initial cluster setup wizard). We had selected LAN1 in this case. I have configured iSCSI MPIO on the ESXi hosts correctly (I do it all the time) and I see multiple active paths, VMware RR is active and IOPS per path are set to 3, etc. BUT, the data flow between ESXi host and Synology happens only on Synology LAN1 and the other LAN ports remain idle. How can we get other other LAN ports to play here?

I tried to become clever and assigned the other network interfaces (LAN2, 3 and 4) a manual cluster IP address (after enabling SHA) and used those addresses in the static discovery of iSCSI port binding. This way I was able to get MPIO working BUT only when writing to Synology (although little flaky). When reading from Synology it defaulted only to LAN1 and could not exceed 1Gbps.

I also tried bonding LAN1, 2 and 3, reconfigured HA and tried to get iSCSI MPIO to work but it didn't as expected. MPIO and bonding (teaming, LAG, etc.) does not work together.

MPIO is meant to utilise multiple network interfaces. This worked fine prior to enabling SHA as we could connect to individual IP addresses of network interfaces. I can't believe that iSCSI MPIO is not fully supported when SHA is enabled! Any ideas or any one of you have experienced similar issues?

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Re: iSCSI MPIO configuration in a HA cluster?

Unread post by syno.dustin » Mon Oct 17, 2016 7:40 pm

It's supported and even mentioned in the white paper: ... _Paper.pdf
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Re: iSCSI MPIO configuration in a HA cluster?

Unread post by Lacroix2k3 » Wed Jun 14, 2017 2:34 pm

Have you find a way to solve it ? We have the same issue with two RS3617xs+ in HA.

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Re: iSCSI MPIO configuration in a HA cluster?

Unread post by Yalp » Fri Oct 20, 2017 6:12 pm


Same setup and issue with a pair of RS815RP+ in SHA. Any help would be appreciated.

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Re: iSCSI MPIO configuration in a HA cluster?

Unread post by ensermo » Wed Nov 01, 2017 3:25 pm

I know this is an old topic but currently we have the same setup.

I can find information on how to setup
Synology HA Cluster and iSCSI MPIO from VMware to single Synology DS1817+

But the only information I could find in a in the HA document regarding iSCSI multipath was:

Implementation for iSCSI storage
Connecting a host to more than one of the storage system’s front-end ports is called “multipathing.” By
implementing Multipath I/O (MPIO) or Multiple Connection per Session (MC/S) on the iSCSI connection, you can
deliver a high quality and reliable storage service equipped with failover and load balancing capabilities, which is
also one of the best practices for IT environments. When implementing an iSCSI multipath network, network
switches should be configured on separate subnets.

Can anyone from Synology explain the last sentence with an example?

I think what (like jsingh did in the first post ) that you need to log into the cluster and enable HA IP on each connection.

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Re: iSCSI MPIO configuration in a HA cluster?

Unread post by HarryPotter » Wed Nov 01, 2017 7:41 pm

ensermo wrote:Can anyone from Synology explain the last sentence with an example?
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Re: iSCSI MPIO configuration in a HA cluster?

Unread post by Thomymaster » Mon Dec 18, 2017 12:04 am


What they mean is that if you setup MPIO (multi-path IO) ISCSI than you should use either 2 different switches for this approac or use one switch with 2 different VLANs. These networks should have separate IP ranges of course


Synology NIC0 ( -> switch VLAN 100 -> ESXI vmnic0 (
Synology NIC1 ( -> switch VLAN 101 -> ESXI vmnic1 (

Then you select "round-robin" as the ESXI multipath policy so that the IO will be splt (every 1000IOPS i think) on the 2 links.

Use the above setup (MPIO) and don't use network redundancy measures like link-aggregation (LACP/802.3ad)

Hope this helps ;)




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