Questions regarding multipathing to a singlecontroller/dual NIC Synology iSCSI NAS

[PePierias]

Hello all,

I've successfully set up iSCSI access to a Synology iSCSI NAS (1619xs+) utilizing a single physical NIC from ESXi. I've set both the vnic and the nic from the synology side to be on a separate VLAN on our physical switch. It worked like a charm!

Now I'm trying to accomplish the same feat using multipathing (both esxi node and Synology have 2 NICs for the purpose). I've read VMware docs and saw a number of youtube tutorials.

I've created a vswitch with two port groups and assigned to each port group a single NIC, with the other set to unused. I've added them to the software iSCSI adapter and both vnics show up as compliant. So far so good.

What I'm failing to grasp is how to assign ip addresses in order for multipathing to work. The Synology NAS is effectively a single controller NAS, with two physical NICs. So far I don't know which of the following approaches should be followed, apart from the fact that I'll use two switches to do the job:

1) set up Synology to have two different ip addresses on the same subnet (note: this is something that I did not understand clearly from the vmware documentation, since it seems as though it is possible to have both IPs on the same subnet). Say 192.168.100.10/24 and 192.168.100.11/24. This effectively means that I'm having two portals, on the same subnet.

Then set the first vmkernel interface from my iscsi switch to have an ip of 192.168.100.1/24 and the second vmkernel to 192.168.100.2/24 (effectively all IP addresses are on the same subnet). The idea in this approach is that both vNICs can access both portals and, in turn, this should allow 4 iSCSI sessions (2 bound vmkernel ports times 2 targer portals each):

- vmk1 (192.168.100.1/24) to portal1 (192.168.100.10/24)

- vmk1 (192.168.100.1/24) to portal2 (192.168.100.11/24)

- vmk2 (192.168.100.2/24) to portal1 (192.168.100.10/24)

- vmk2 (192.168.100.2/24) to portal2 (192.168.100.11/24)

Is this scenario plausible? It's definitely not working though: I can see that the targets exist, but no path is created...

2) set up 2 VLANs, say storage1 and storage2. Set up Synology to have two different ip addresses on different subnets, say 192.168.100.10/24 and 192.168.200.10/24. Connect the first to the storage1 vlan and the second to the storage2 vlan.

Set vmkernel1 and vmkernel interfaces to be also on different subnets, but each one in the same subnet as the respective Synology NIC. For example, 192.168.100.1/24 and 192.168.200.1/24 and connect them to storage1 and storage2 vlans, respectively.

In this setup I suppose there would be two paths:

- vmk1 (192.168.100.1/24) to portal1 (192.168.100.10/24)

- vmk2 (192.168.200.1/24) to portal1 (192.168.200.10/24)

Important: my esx node has a management vmkernel interface on a 10/8 interface. But I suppose that should not present an issue here, since access to the portals is non-routed.

Which approach should I pursue? Any idea or pointers here would be helpful.