Designing vSphere for 10Gb converged networking, with Cisco UCS, Nexus 1000V and NetIOC

Whilst working on a Vblock 300 implementation a few weeks ago I had an interesting conversation with one of the network architects at VCE and we discussed the subject of best practices surrounding 10Gb and 1Gb networking. Traditionally with 1Gb networking it is best practice to separate traffic on your ESX/ESXi hosts with vSwitches (or dvPortGroups) dedicated to each type of traffic (vMotion, Management, Storage, production networking) and typically designs will contain 6 to 8 NIC’s per host. With the introduction of 10Gb networking, I’ve noticed that some implementations have neglected to include some important design considerations regarding the use of 10Gb networking. Lets say for that we present 4 x 10Gb NIC’s to each host (these are vNIC’s in the Cisco UCS world) or we can present 6 x 1Gb NIC’s  using traditional methods of separating the traffic into various dvportGroups. Which is best?  Can we get away with just 2 x 10Gb NIC’s or do we need more? The key consideration here isn’t how many NIC’s (or vNIC’s) are presented to each host, but rather how much network bandwidth is available to each traffic type (i.e. vMotion, FT Logging, VM traffic) and critically how we control it.