Does the subject make any sense ? hmmmm.. I dont know .. It is upto your decision, because this is one of the question which I get normally from people when they hear about RHEV or if you explain about it ..
I will try to put these components in simple terms, if I fail, poke me with your comments..
KVM is a hypervisor , well yeah.. strictly speaking I have to tell that, kvm makes/turns a linux system as a hypervisor.. Thus allows you to run virtual machines inside it.. Oh.. yeah.. I have heard that .. but then what is ‘libvirt’?
libvirt is an API which allows you to talk with your hypervisor.. The applications like ‘virt-manager’ can take help from libvirt to talk to the hypervisor ( ex: kvm) .. Thus manage virtual machine..
From above, you understood that, if you have a linux kernel running in your machine KVM can host VMs and applications like ‘virt-manager’ can be used to administer it..
Then, how RHEV is related to KVM ? well, if you view a RHEV environment in your mind, it would look like this.
[ Hypervisor 1] <———-> [ RHEV-Manager] <———> [ Hypervisor 2]
Very bad ascii art ? I feel so.. nm 🙂
How this hypervisors are made ? again KVM makes this hypervisor .. These hypervisors contact/talk to RHEV-Manager server.. What is the communication channel between these hypervisors and RHEV-manager? It is a service called “vdsm” Ok.. sounds good.. In that case , no “libvirt” ? hmmm.. RHEV2 setup was not using ‘libvirt’ in RHEV hypervisor, but RHEV3* make use of libvirt service.. In RHEV3 context “vdsm” , trigger libvirt for VM life cycle operations.. but still, vdsm is the communication agent between rhev hypervisor and RHEV-M..
RHEV hypervisor can be a RHEL system with kvm modules loaded.. Otherwise a ‘live CD’ image called RHEV-H can act as a hypervisor.. RHEV-H does not differ from a RHEL hypervisor in terms of kvm or vdsm.. Just think RHEV-H as a live CD image with minimal size. It is a dedicated appliance and not supposed to run other applications like RHEL hypervisor.
We talked about RHEV-Manager Or RHEV-M , but what is it ?
In simple terms, it is the managing server.. Think of it in terms of a ‘administration’ server.. In fact a GUI installed server 🙂
Finally, Do you want a ‘windows server’ in a RHEV environment ? hmmm.. RHEV-Manager in RHEV 2 required it., but latest version of RHEV-3 does not require ‘windows’ server . You can install RHEV 3 Manager in a linux system with a simple command , #rhev-m setup
I am stopping here.. but please feel free to ask your queries , if any.. I would try to explain it in detail.. This is a simple wrap up on KVM and RHEV…
* MODIFIED THIS ARTICLE FOR INCLUDING RHEV 3 BITS