IBM 3650M2 “battery status alert”

There a lot of determining factors that go into the performance feeling here. One tweak you might consider is setting up Jumbo Frames. Scott Lowe has a recent blog post here that shows some of what he did to achieve this.

You mention that the guests will be running low CPU load - those are always great candidates for virtualization - but the difference between FiberChannel and iSCSI doesn't really come into play yet.

If your vm guests are going to be running storage-intensive operations, then you have to consider that the speed of transferring a read/write operation from the VM Host to the storage array may become your bottleneck.

Since your typical iSCSI transfer rate is 1Gbps (over Ethernet), and FC is usually around 2-4Gbps (depending on how much cash you're willing to spend), then you could state that the transfer speed of FC is roughly twice as fast.

There's also the new 10Gig-E switches, but your Powervault and Powerconnect don't support that yet.

However, that doesn't really mean that the machines will work faster, as if they are running applications with low I/O, they might actually perform at the same speeds.

The debate as to which is better is never ending, and it basically will depend on your own evaluation and results.

We have multiple deployments of FC-based mini-clouds and iSCSI-based mini-clouds, and they both work pretty well. We're finding that the bottleneck is at the storage array level, not iSCSI traffic over 1Gb Ethernet.

I use the data coming out of the (i)DRAC, combined with the data that ESXi harvests via CIM, with vCenter configured to alert on faults coming out of the CIM monitoring.

I'm a little unclear on what you're saying about the trustworthiness of the CIM data, but I personally trust it a heck of a lot more than I would trust the SNMP traps being fed to WhatsUp. CIM will catch and throw alerts on something as minor as low voltage on the BIOS battery, as long as your hardware is well supported (as recent Dell equipment is), and vCenter is pretty flexible about choosing what, where, and how often you throw alerts on those events.