ME4024: Cabling dual controllers to a VLT domain.

TLDR - The docs show cabling the controllers in a way that isolates each subnet to a switch. Why? I thought it would be ideal to have a path through each switch to both controllers via both subnets.

Obligatory "I'm not a storage guy" or "Network guy" for that matter.

We're trying to figure out the proper way to cable a dual controller ME4024 storage array to two S4048-ON switches that are configured for VLT (Dell's MLAG). We will be using all four CNC ports on each controller (8 total connections) and two subnets. iSCSI protocol to be used.

The following example from the official documentation has left us a little confused. If we're understanding this correctly, the docs are telling us to cable the CNC ports to the switches in such a way that one subnet is on Switch-A and the other subnet is on Switch-B. Highlights have been added to show subnets 10 (green) and 11 (blue). NOTE: The controller ports are 3, 2, 1, 0 (left to right) btw.

This doesn't make much sense to us. With this configuration I would think that Windows iSCSI initiator would lose connection to some targets...therefor losing connection to some storage. Unless I'm wrong and they won't actually lose access to storage...they'll just lose a path or two.

• Wouldn't you want a path through each switch for each controller AND subnet?
• If a switch is lost in the above example, access to an entire iSCSI subnet is also lost, no?
• Is there a reason for isolating the iSCSI subnets to their own switches?
• Are there different cabling recommendations if the switches are configured in VLT?

Update: Maybe my confusion here is with the subnet. I just noticed that the IP addresses are 192.68.xx.xxx. Am I looking at one 255.255.0.0 subnet in the example then? I wouldn't think so since the table clearly lists 10 and 11 in the subnet column as if they are two distinct subnets. I'm so confused by Dell's documentation.