I agree its probably re-balancing. Will need to see how this changes over the next few days.

I checked the ISL which is 2x1Gbps in a port channel and we're only seeing approx 100Mbps between the two storage switches so I have no concerns there.

There are two Cisco 3560E's dedicated to servicing 2xPS6100's and 2xPS4100's in a full mesh topology, with all connected hosts uplinked to BOTH switches. There is no case where the only path between a host and the storage REQUIRES the ISL (unless there was a NIC failure on a host). I was under the impression that if the ISL ever became oversubscribed and latency increased due to TCP retransmits or pause frames that MEM or Dell's DSM would be able to NLB the sessions accordingly.

It's a difficult statement to back up if there are zero indications of an oversubscribed ISL. Packets per second, megabits per second, interface statistics, buffers, etc, are all well within normal parameters.

I messed up the diagram a little bit when it comes to the active/inactive ports on the PS6100's but you get the idea. 4 active and 4 inactive ports to each switch.

We are distributed correctly for HA.

I drew up a quick diagram:

http://i.imgur.com/HmyAtuJ.png

I'm glad that clarified that. You had me a bit worried even though I was sure it was sufficient (for now). :).

I'll keep an eye on the volume load balancing.