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Catalyst 4948E vs Nexus 3048 for iSCSI

Hi all,

I am evaluating a switch upgrade for one of my networks as part of a SAN upgrade.  I have 6 x VM hosts with 8 NICS each plus a handful of other servers.  My current SAN has 8 x 1gb drops.  We are running some 3 x 48 port HP switches, with all of the VMWare and iSCSI traffic on the 'central' pair of switches and ilo and some less important servers single homed on a 3rd switch (due to lack of available ports). 

The new SAN will have 10GB iSCSI links so the plan is to get a pair of 48 x 1gb + 4 x 10gb port switches.  We would use 2 x 10gb ports per switch for the SAN and 2 as cross switch links.  We would also buy a 3rd switch for our less important servers in much the same way we have now.

I see recommendation for the Nexus 55xx series switches but that is out of our price range.  We have been looking at the Nexus 3048 and the Catalyst 4948E.  We had also evaluated the Catlyst 3750-X but got several points of advice that it was not sufficient for iSCSI traffic

My primary concern is around buffering and queuing of the 10gb san <-> 1gb iSCSI host data.  I have seen discussion about the 3048 being a cut through switch vs 4948 being store and forward.  cut through seems best on latency but when managing the speed transition, it seems like both will effectively be a store and forward, right?  the 4948E seems to have a larger buffer. Is there anything that should sway me towards one switch or the other?

Much further down the importance list is a second question.  If we do go w/ the 3048 (where we are leaning right now), I was planning to make the 'central' pair a vPC peer.  I would like to connect my 3rd switch to both central switches. Afaict, there is no way for me to have 3 switches in the same vPC peer group.  What would be the best way to accomplish this, portchannel?  Or is there something fancier I should look into? 

Thanks in advance for any suggestions

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