After installing OpenStack and posting a few articles, I started to dig down a bit more on the KVM hypervisor used in OpenStack. For that, I wrote about the libvirt API and how to remotely manage KVM with it.
In this article, I will introduce how KVM is used in Openstack and what a virtual machine is made of.
How A Virtual Machine Instance Comes to Life?
As discussed in my previous post, Libvirt is an open source project for managing hypervisors. With the increasing popularity of Openstack, it’s important to get familiar with KVM as an alternative virtualization platform to commercial products like vSphere and Hyper-V.
To use KVM, you don’t have to install Openstack – you can just install KVM as a standalone product as described in my previous post. In that, it’s pretty much like VMware Player or Workstation. In terms of maturity, KVM is pretty solid and way ahead of Openstack which is also improving quickly since last year with many commercial vendors jumping in.
While working with Openstack on both VMware virtual machines (with no virtualization instruction set exposed) and physical machines, I found virtual machine instances can be deployed seamlessly. On a machine that does not have virtualization instruction set exposed, KVM falls back to QEMU silently. That is why could I try out OpenStack on virtual machines before my hardware was ready. Because both KVM and QEMU support the same libvirt APIs, you would not notice any difference using command line like virsh, or Virtualization Manager. That is the beauty of standard APIs with different implementations, similar to the standard vSphere APIs that are implemented by both vCenter and ESXi.
As mentioned earlier, I got the KVM instances running on my compute cluster after installing the Openstack. I’ve been curious on KVM management APIs, so I took some time to give it a try. In the following, I’ll detail on how to set up environment and get your first HelloWorld type of Java code working.
After installing Openstack, I got KVM/QEMU installed as a by-product. To get myself familiar with the functionalities, I played with Virtulization Manager and the virsh command line. By comparing with the libvirt API, I found they are pretty similar. Therefore, I think it’s a good starting point before jumping to the APIs. Also, the virsh is implemented on top of the libvirt APIs.
Having successfully installed OpenStack all-in-one with PackStack, I started to try out the multi-node deployment. It ended up much longer time than I thought because of various issues mainly with networking. The following summarizes what I did to make it work, and some tricks and tips I found out during the process.
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