In the early days of Linux, it was often the technical people in organizations who knew about it and were already implementing, while management had little awareness of Linux. We are seeing that same trend occurring now with KVM. To help further the overall understanding and awareness of KVM and fill in the information gap, here is a list of the most frequently asked questions that we at IBM have encountered in recent panel discussions, conversations, and interviews.
FAQ 1: How does KVM fit in with cloud?
Virtualization is overwhelmingly used for cloud computing, and open virtualization enables open clouds. KVM is an open proven, enterprise-ready virtualization technology that helps enable interoperability and portability so customers can avoid vendor lock-in.
But, as cloud computing becomes more accepted, the focus is also shifting to cost containment, making KVM a desirable addition to data center environments. For cloud service providers in particular, cost efficiency is important so that they can provide services at reasonable prices. Important advances have also been made in management solutions that enable KVM to be controlled alongside other virtualization technologies like VMware. For example, IBM Systems Director VMControl enables the management of virtual environments across multiple virtualization technologies and hardware platforms.
How enterprise-ready is KVM? IBM uses KVM in its public cloud - IBM SmartCloud Enterprise - and our own IBM Research Compute Cloud (RC2), a private cloud for internal IBM, also relies on KVM for its virtualization.
In addition, IBM customer Dutch Cloud is a cloud service provider in the Netherlands. Open standards are very important to Dutch Cloud, and being able to support both KVM and VMware hypervisors with IBM SmartCloud Provisioning enables them to offer choice to their clients. “KVM also saves us a lot of money, because of its lower licensing costs. We are using both KVM and VMware, so IBM SmartCloud Provisioning enables us to bring in customer environments on VMware and reduce costs by moving them to KVM. We’ve also found KVM much easier to install and manage,” explains Martijn van Zoeren, CEO, Dutch Cloud, in a customer case study.
For more information, go to Jean Staten Healy’s blog about KVM and the cloud, Why Open Virtualization is Important for Cloud.
FAQ 2: KVM currently has a small market share. Don’t the other hypervisors have too big a market share for KVM to have any chance of success?
The computer industry is full of examples of new technologies which started with small market shares overtaking entrenched competitors.
According to analysts, only one in five physical servers are virtualized so far – meaning there is plenty of headroom because many clients are still making their virtualization decisions. In addition, customers are fearful of vendor lock-in with proprietary solutions. With the availability of new management tools - such as IBM Systems Director VMControl that covers both proprietary and open source virtualization technologies - heterogeneous virtualization is becoming a much more realistic choice.
Customers like choice and lower costs – as long as the alternative is still enterprise-grade. Linux and Eclipse succeeded through a combination of great technology, a compelling customer value proposition, and an open approach not dominated by any single vendor. KVM has all of these attributes
The market share gain for KVM is likely to be driven by users with affinity to Linux and open source - customers who feel that are paying too much for their current virtualization approach, and by service providers implementing cloud computing who want a cost-effective, secure, and scalable virtualization option.
In addition, KVM has a number of advantages compared to other hypervisors. KVM currently holds the top seven SpecVirt virtualization benchmark. These all use Intel processors and Red Hat virtualization, and are a mixture of HP and IBM systems. On the same 2-socket and 4-socket hardware, KVM delivers slightly better virtualization performance than VMware. But where KVM really excels is on scalability. Only KVM has published SpecVirt benchmarks for 8-socket, 80-core systems, since it can scale much better than VMware and support many more processors and larger memory, because it inherits the scalability of Linux. This translates to greater virtual machine density on large x86 systems, and therefore better resource sharing and lower costs.
KVM also inherits the Mandatory Access Control of SELinux (Security Enhanced Linux), and uses it to provide a very high level of security between virtual machines. This means that clients can be confident that their data and applications are fully protected, even in a multi-tenant cloud environment. Only KVM has this level of hypervisor security, which it inherits from Linux. In addition, KVM has recently been certified at EAL4+ level in the Common Criteria security certification, with RHEL 5 and IBM servers, and is currently in evaluation with RHEL 6. This gives government and other security-conscious clients the confidence that KVM has been tested at a top security level.
KVM also inherits quality of service features from Linux, including cGroups which enable resources such as processors and memory to be allocated to specific virtual machines, thus ensuring that high priority virtual machines get the resources they need.
Customers are looking for an open alternative to proprietary virtualization solutions, and KVM provides an enterprise-ready option.
KVM is being used for cloud computing because cloud service providers, both public and private, are looking to minimize their costs – by increasing the density of virtual machines on each physical server and by reducing the software licensing costs of the hypervisor
KVM is also being used for Linux server consolidation. Linux servers are currently less virtualized that Windows servers and KVM is the natural choice, since it is already integrated as part of the leading enterprise Linux distributions from Red Hat, SUSE and Ubuntu
And, KVM is also being used by enterprises with heterogeneous virtualization. Large enterprises that are already using VMware and are comfortable using multiple hypervisors are now adding a new wave of virtualized servers. Adding KVM into their data center environments has become a much easier decision to make now that multiple hypervisors can be managed from a single management console.
5-How does KVM fit in with the OVA, oVirt, OpenStack, and the rest of the virtualization community?
Open source is all about community – KVM is the latest example. The Open Virtualization Alliance (OVA) is a marketing alliance, aiming to promote KVM and open virtualization technologies. The code development happens in open source communities, including KVM and oVirt.
The KVM community develops the base hypervisor, while oVirt develops the virtualization management software and also packages the hypervisor and management software together. KVM is also included into the Linux source code development tree, rather than being a separate add-on, so it is fully tested and integrated
Open Stack is a cloud infrastructure that is hypervisor-agnostic. OpenStack was originally developed on KVM, but it has now added multiple hypervisor support. OpenStack also uses the native hypervisor management tools – for example using oVirt to deploy, start and stop virtual machines. In addition, oVirt enables fine-grain control of KVM – to enable a work group/resource pool sized infrastructure. It also includes automation, but offers a lot more detail that you can monitor because virtual machines need more granularity in management.
6-Does KVM have vMotion or live migration?
KVM has always had live migration – from the very beginning - but some people don’t know that it has that support. So yes, it does and it has almost the same features that VMware has. It is still missing some of the storage features and the storage APIs but the community is already working on these and plans to remedy the gaps very soon. There is upstream development information available about all of these.
7-How does KVM differ from Xen? Why did IBM stop working on Xen and start working on KVM?
Dan Frye actually offers a great explanation of this in his blog, On the Origin of KVM. It is true that IBM was a major supporter of Xen for a time. To recap briefly, it comes down to community and technology. In terms of community, the big difference between KVM and Xen is that KVM is really a community where lots of people are contributing it and it is not tightly controlled by one owner. In terms of technology, the big difference between KVM and Xen is that KVM leverages the Linux kernel for all types of services, so a lot of work that has already been done for Linux can be leveraged for KVM, rather than writing code from scratch. At IBM, we invested a lot of time in submissions to Xen which were rejected but were very similar to submissions that were put into Linux and were important to making Linux more scalable.
Program Director, Linux and Open Virtualization Strategy, IBM