MSA2012i - effects of using same subnet for both failover pairs

[Zouleous]

IP Address scheme for the controller pair

The MSA2012i uses port 0 of each controller as one failover pair, and port 1 of each controller as a second failover pair. Therefore, port 0 of each controller must be in the same subnet, and port 1 of each controller should be in a second subnet. For example:

Controller A port 0: 10.10.10.100

Controller A port 1: 10.11.10.120

Controller B port 0: 10.10.10.110

Controller B port 1: 10.11.10.130

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That is the information I found in the documentation.  I notice it says port 1 of each controller SHOULD be in a second subnet.  Can anyone explain why this is important and what effect it would have if I was to put everything in one subnet.  I do have them on different switches, but the switches are linked.  Thank you.

[Zouleous]

Just to be clear I would like to have them connected the way the documentation suggests.  I have to come up with a good reason to convince my network guys that it is necessary.  Right now I don't know enough to make a good arguement.

[Kenneth Carlile]

I struggled with this myself, and I think the best answer is that if something on a single iSCSI subnet goes berserk and starts broadcasting like crazy (namely a broadcast storm), the whole shebang goes down. On the other hand, if you've got two networks, while you lose one network to something like that, the other will stay up--even if the subnets are routed to each other. 

[Zouleous]

So it doesn't affect the functionality of it then?  It's just to protect you from issues on that subnet?  I think I'm going to have a hard time convincing our network guys to set up another iscsi subnet for that reasoning unformately.

Does anyone else know of any other reasoning?  Thanks.

[Zouleous]

this was the only reasoning I ever found:

http://support.microsoft.com/default.aspx?scid=kb;EN-US;175767