SAN, ISCSI and Multipath (MLAG?)

Solution 1:

Since you have iSCSI SAN, I suggest you go with MPIO splitting iSCSI networks and utilize different subnets. LACP does same failover as MPIO, however comes with performance penalty due to unsupported Multiple Connections per Session (MCS) meaning, it would not performance boost for same configuration. https://www.starwindsoftware.com/blog/lacp-vs-mpio-on-windows-platform-which-one-is-better-in-terms-of-redundancy-and-speed-in-this-case-2

Tweak the performance configuring NICs and switches Jumbo Frames value of 9k.

Solution 2:

This is a case where you should follow your storage vendor's guidelines.

I don't know who will be consuming your SAN resources, but the general approach should be:

• Your regular servers using LACP should have LACP bonds comprised of links to both switches.
• Your MLAG should have some sort of cross-switch peer link.
• Your iSCSI should be delivered via MPIO, using one or more ports from one controller to one switch on a specific VLAN, and one or more ports from the other controller to the other switch on a different VLAN.
• Those iSCSI VLANs should be unique to each switch and not participate in the MLAG.
• If your servers will be using iSCSI directly, go with the MPIO approach... two VLANs and one port from the server to each switch. This may complicate normal data if you only have two ports per server.