Tuesday, February 24, 2009

Red Hat Goes Streaking - Dumps Xen

Yesterday Red Hat announced their revised virtualization strategy. Most interesting to me was Red Hat's declaration that the hypervisor should indeed lie "naked" on the metal. Red Hat also announced end-of-life for Xen support and some stuff regarding desktop virtualization and protocols that I don't pretend to understand. While it was expected that Red Hat would end-of-life support for Xen after their acquisition of the KVM technology from Qumranet, the fact that Red Hat went streaking into the market with a bare metal approach to the hypervisor was a pretty significant strategy reversal.

Until yesterday, Red Hat had always adopted the Microsoft line on the hypervisor - it is simply a feature of a general purpose operating system. Red Hat historically claimed that the hypervisor should not lie naked on the bare metal, but instead it should be wrapped up inside the general purpose OS - a little extra bloating that never hurt anybody. It looks like some combination of market forces - likely VMware financial success and Amazon's adoption of Xen for their Elastic Compute Cloud - have forced Red Hat to consider a new approach. Now Microsoft stands alone in their contention that a hypervisor is just a new general purpose OS feature, and the rest of the market can move on to the market share land grab for the large-scale Linux datacenters. It should be an interesting race, because all three players - Xen (Citrix), KVM (Red Hat), and VI (VMware) are all coming from different positions of strength - and weakness.

In almost every case I have observed, Xen is the incumbent virtualization technology among the Linux datacenter consumers that have virtualized any production workloads. However, not many have actually virtualized because the historical compelling case for virtualization - server consolidation - falls on deaf ears among the Linux crowd. With Linux, as opposed to Windows, it is possible to run multiple application workloads on a single server without significant instability. Server utilization can be quite high without virtualization - hence no requirement for Linux server consolidation. But, the new benefits of virtualization - flexibility, security, and elasticity - apply equally, if not especially, well to the Linux workloads. If application workloads are separated into unique, small footprint, virtual machines (virtual appliances, if you like) that run atop a bare naked hypervisor, then:

- flexibility is better because one application can be managed/administered without interfering with another workload running on the same host

- security is better because vulnerable services like DNS are isolated and easier to maintain/secure due to a smaller footprint

- elasticity is better because application workloads can be scaled quickly when demand increases and also retired quickly when demand recedes (cloud, anyone?)

Because of these new business benefits, Xen is beginning to take hold in the Linux datacenters. Citrix, however, has not historically been a strong brand among the Linux savvy crowd, so it is unclear if they have the stomach for pursuing a new market segment. VMware is the 800 pound gorilla in hypervisors generally, but they too have shown very little Linux savvy (their management console only runs on Windows) - probably because 90% of their revenues come from virtualizing Windows workloads. Then there is Red Hat, the 800 pound Linux gorilla who has been in denial about the importance of a bare metal approach for the hypervisor - until now.

Based on this set of circumstances, I would say that the virtualization opportunity for the Linux datacenter market is a wide open race. Now that Red Hat has decided to run the race naked, it should be more fun to watch.

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At 11:39 AM, Blogger alq666 said...


My understanding of Xen vs. KVM is that Xen is a bare metal hypervisor that runs a OS to manage resources as a slightly more privileged guest than others, whereas KVM rolls out virtualization on top of the linux kernel (i.e. not on bare metal). RedHat's white paper seems to corroborate that KVM lives in/above the linux kernel as opposed to having the linux kernel run in the hypervisor (http://www.redhat.com/f/pdf/virtualization/RH_VirtLaunch_ExtendingReach_wp_964722_0209AY_web.pdf). From KVM's documentation: "[KVM] consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-intel.ko or kvm-amd.ko".

Am I misunderstanding your comments on RedHat's latest announcements?

At 1:50 PM, Blogger Billy Marshall said...

In the case of KVM, the Linux kernel plus a module IS the hypervisor. My comments were directed at Red Hat's historical marketing approach, where they declared that the hypervisor was a feature of a general purpose OS. They historically required you to purchase the OS in order to get the benefit of hypervisor support.

Now, they are going to sell the hypervisor independent of a purchase of the general purpose OS. This is the big change. The technology is fundamentally the same architecture as always.


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