CPU Resource pool with and without hyperthreading in vmware esx/esxi

I've only read about this topic a handful of times. I found an article at www.vmguy.com here that sums up the consensus on this HT issue (direct from the article):

There are pros and cons to using HT in ESX.

Pros

• Better co-scheduling of SMP VM’s

  Hyperthreading provides more CPU contexts and because of this, SMP VM’s can be scheduled to run in scenarios which would not have enough CPU contexts without Hyperthreading.

• Typical applications see performance improvement in the 0-20% range (the same as non-virtualized workloads).

Cons

• Processor resources are shared with Hyperthreading enabled

Processor resources are shared such as the L2 and L3 caches. This means that the two threads running on the same processor compete for the same resources if they both have high demand for them. This can, in turn, degrade performance.

All things considered, it is difficult to generalize the performance impact of Hyperthreading. It is highly dependant on the workload of the VM. One additional point is that you can always utilize the CPU min and max values on a per-VM or Resource Pool basis to reserve certain amounts of CPU for your most critical workloads. As with the majority of performance items I enounter, test, test, test. Try out the workloads and see what works the best on the hardware you have available.

Again, this is directly from the article. I'm not certain that HT is worth it as I too use AMD Opterons so I can't speak from experience.

The RAID on that motherboard is not real hardware RAID, it's "fakeraid" that depends on drivers in the operating system. ESXi doesn't support fakeraid, because it's aimed at enterprise environments (which use real hardware RAID for better performance), not consumer PCs (which use fakeraid because it's cheap). ESXi should recognize drives connected to that controller, but only as standalone drives, not as a RAID array.

You might want to opt for a different virtualization platform, such as Citrix XenServer or Linux KVM. If you really want to use ESXi, you could set up your three drives as separate datastores, give each of your VMs three virtual disks — one from each datastore — and set up software RAID within each VM's operating system.

(The VMs will not be able to see the host's fakeraid controller. Isolating guests from the host's hardware is half the point of virtualization. Guests will only see their virtual disks.)

There are unofficial drivers that you can install on ESXi to support additional hardware, including a "dmraid" one for Intel Matrix RAID (your chipset's fakeraid), but you're going out on a limb if you do that.