Difference between KVM and RHEV/OVIRT

Does the subject make any sense? hmmmm.. I don’t know. It is up to your decision because this is one of the questions which I get normally from people when they hear about Ovirt/RHEV ( RHEV is downstream/product offering from Red Hat based on upstream or community project called ovirt) 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. Sure, maybe you have heard that .. but then what is ‘libvirt’?

Libvirt is an API that 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 life cycle ie nothing but creation, managing and additional features like migration..etc.

From the above explanation, you may understand that, if you have a Linux kernel running in your system/machine KVM can host VMs ( virtual machines), and applications like ‘virt-manager’ can be used to administer it with the help of a library or API called `libvirt`.

Then, how Ovirt/RHEV is related to KVM? well, if you take a picture of an Ovirt/RHEV environment in my mind, it would look like this.

[Hypervisor 1] <——> [ Ovirt Manager/RHEV-Manager] <——-> [Hypervisor 2]

How these hypervisors are made? again KVM makes this hypervisor .. These hypervisors contact/talk to RHEV/Ovirt-Manager server. What is the communication channel between these hypervisors and Ovirt/RHEV-manager? It is a service called “vdsm” Ok.. sounds good. In that case, no “libvirt”? hmmm.. RHEV3 or the latest version of Ovirt makes use of Libvirt service. In RHEV3 context “vdsm”, trigger libvirt for VM life cycle operations. but still, vdsm is the communication agent between ovirt/rhev hypervisor and RHEV-Manager/Ovirt-Manager

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 Ovirt-Manager/RHEV-Manager Or Ovirt-M/RHEV-M, but what is it?

In simple terms, it is the managing server. Think of it in terms of an ‘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 the latest version of RHEV-3/Ovirt does not require the ‘windows’ server. You can install RHEV3/ovirt Manager in a Linux system with a simple command,

[terminal]
#rhev-m setup
[/terminal]

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/Ovirt…

ps# RHEV2 setup was not using ‘libvirt’ in RHEV hypervisor,

Copyright secured by Digiprove © 2020 Humble Chirammal