AWS, the world’s largest public cloud vendor, recently announced a new C5 instance that is entirely based on the new virtual machine Hypervisor: KVM. For the previous 11 years, all instances of AWS virtualization were implemented based on XEN technology. In other words, AWS is starting to go the KVM route instead of sticking with the XEN technology it has been using since its inception.

We know that virtualization is the core technology in cloud computing (note that there is no one here). Switching the core virtualization engine from XEN to KVM presents huge challenges in terms of underlying technology, product architecture, and user experience.

Like AWS, Ali Cloud experienced severe external and internal pains in switching from XEN to KVM. At that time, there were no obvious industry cases to refer to, and the technical progress of XEN community was still in full swing. More importantly, the change of underlying core technology would bring extremely violent impact on several core modules in the whole cloud architecture, such as control system, virtual storage, virtual network, system management and operation and maintenance. It can be said that the whole body is involved.

But a few things during the experience, let our virtualization technology director – Zhang Xiantao decided: “now, it is time to make their own choice!”

1) As X86 processors (VT-X, EPT, VT-D) increasingly support virtualization, the performance advantages of XEN paravirtualization are gradually losing, but due to its structural complexity, ali Cloud secondary development and maintenance have brought great challenges. 2) THE KVM project is gradually maturing. KVM is widely recognized in the industry because of its simple architecture and the reuse of Linux kernel logic, making the code simple and efficient. 3) The Xen XSA-108 vulnerability broke out in 2014, AWS and LINODE restarted a large number of physical machines. Although Ali Cloud made online repair through an innovative solution at that time, it also took a lot of energy and time.

Teacher Ma said, “Seeing by believing.” The phrase is applicable here. We believe in the firsthand experience of front-line R&D engineers; The belief that a technology will evolve from imperfect to perfect; Believing in the right direction is the most important thing, even if it requires us to go through as many holes as we can!” Today, we are beginning to enjoy more and more overall r&d efficiency, system efficiency/performance advantages due to the superiority of the underlying architecture. These contents will be introduced one by one in the following special articles.

Ok, now we can move on.

1. Do you know when Aliyun switched from XEN to KVM? How long has XEN been used in Aliyun before this?

2. As a user, have you ever been troubled by the switch of the underlying technology of Ali Cloud? Or what needs to be improved at this stage in terms of underlying virtualization?

3. Describe the advantages of KVM virtualization as you understand it.