Answers/Opinions:
1) Nesting speed -- Nested VMs will run at less than half the speed the VM would run if it ran as a VM that wasn't nested.
2) CPU feature set needed to do nested virtualization -- the CPU feature you need is SLAT -- don't buy any CPU that doesn't have SLAT capability (this would be named EPT in Intel CPUs and named RVI in AMD CPUs).
3) Server based or white box based -- If you're looking for white box information, there's a white box list of compatible motherboards for use with ESXi available on the Internet (inserted into next post).
As far as server based hardware, it will do what you're wanting with Nesting and it's available cheaply on eBay. These will have more memory capacity (usually the biggest constraint for virtualization).
If you're budget constrained and only need a small lab setup for instance (without a huge amount of memory capacity), an AMD HP DL385 G2 with a BIOS upgrade and 2.3 GHz Opteron 23xx/83xx CPUs of Stepping 2 or higher will do nested hypervisors (ESXi 5.x, Hyper-V and XenServer and KVM) and those hypervisors will run their own 64 bit VMs.Max memory in that budget nesting-capable server is 8x 4GB ECC Registered non-FB PC2-5300 sticks of memory. The server on eBay can be purchased for under $150. You add 2x quad-core Opteron 2356 CPUs Stepping 2 or higher ($10 each on eBay) and memory.(32GB 8x 4GB ECC Registered non-FB memory is $70 on eBay). Boot ESXi from a USB stick and RAID some SAS or SATA drives in the HP server. Get a NetApp storage appliance downloaded (good for 150 calendar days with subsequent licenses put into it occasionally) so you can share out your SAS or SATA disks as shared storage to your nested hypervisors.
4) AMD -- Yes, AMD server-based CPUs can be used (Opteron 23xx/83xx Stepping 2 or later) as well as 24xx/84xx and 41xx type -- your AMD server needs to be able to handle one of these types of CPU families. If you're looking for white box information, there's a white box list of compatible motherboards for use with ESXi available on the Internet (inserted into next post).
5) Networking Tip for Nesting ESXi -- Make sure you utilize VSphere Distributed Switches for everything with your nesting cluster setup so you can engaged NIOC (Network IO Control) -- that will make nesting networking run so much better for you.
Hope that helps.
Datto
