Sorry as I'm kind of new to forums so I'm not sure if this is the correct section...
Anyways, I would like to set up a little virtual lab using a type 1 hypervisor and am trying to decide whether I should use XenServer/XenCenter or ESXi/vSphere... What are the advantages and disadvantages of each, which offers a smoother experience when using the virtual machines? Are there any "missing features" in either that I should be aware of? Thanks a bunch for your input!
"Type 1" hypervisors are a deceptive name. People generally think that they offer better performance because they have no underlying operating system running. But the fact of the matter is, that kvm on linux uses the same kernel for the system and the hypervisor, including the IO scheduler of the kernel, whereas "type 1" hypervisors, do not always do that. and the end result is ALWAYS that the performance in kvm beats ANY "type 1" hypervisor, plus it obviously offers the benefit of extra functionality that it can add, like QEMU hardware emulation or manual configuration.
On the other hand, kvm also offers automatic startup of the guest, or "booting into the guest", with a minimal host overhead, and that overhead, can be so much less than with "type 1" hypervisors. So kvm is the best of both worlds, it offers better "type 1" performance than ESXi and Xen, and it offers more "type 2" features than HyperV or VMWare.
The biggest benefits that kvm has besides speed, is that it allows for the use of a more modern guest, that it is entirely free and open source software, and that it offers the benefit of the extra security options in the underlying (minimal if you want) OS.
To be honest, no hypervisor offers a host system of the same quality as linux. The main sales argument is that "you don't see the underlying OS", but no commercial "Type 1" hypervisor goes as far in using the bare metal kernel and hardware as KVM, and with kvm, you can perfectly configure a host to start up automatically at boot, which delivers the same "experience" as a "Type 1" hypervisor, just faster, and with the option of enhanced security and flexibility.
ESX is used a lot in the enterprise world, but it's still closed source software. Xen is less closed source software, it's also faster than ESX, but it's not running as "native" as kvm. Kvm is really by far the best solution, regardless of how you look at it, and it's obviously also completely free, it doesn't cost anything.
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I've just moved all my VMs over to KVM thanks to this, so thanks :)