Inside System Storage -- by Tony Pearson

Since the [IBM System Storage Technical University 2011] runs concurrently with the System x Technical University, attendees are allowed to mix-and-match. I attended several presentations regarding server virtualization and hypervisors.

Hypervisor Architecture

Matt Archibald is an IT Management Consultant in IBM's Systems Agenda Delivery team. He started with a history of hypervisors, from IBM's early CP/CMS in 1967, through the latest VMware Vsphere 5 just announced.

He explained that there are three types of Hypervisor architectures today:

• Type 1 - often referred to as "Bare Metal" runs directly on the server host hardware, and allows different operating system virtual machines to run as guests. IBM's System z [PR/SM] and [PowerVM] as well as the popular VMware ESXi are examples of this type.
• Type 2 - often referred to as "Hosted" runs above an existing operating system, and allows different operating system virtual machines to run as guests. The popular [Oracle/Sun VirtualBox] is an example of this type.
• OS Containers - runs above an existing operating system base, and allows multiple "guests" that all run the same operating system as the base. This affords some isolation between applications. [Parallels Virtuozzo Containers] is an example of this type.

The dominant architecture is Type 1. For x86, IBM is the number one reseller of VMware. VMware recently announced [Vsphere 5], which changes its licensing model from CPU-based to memory-based. For example, a virtual machine with 32 virtual CPUs and 1TB of virtual RAM (VRAM) would cost over $73,000 per year to license the VMware "Enterprise Plus" software. The only plus-side to this new licensing is that the "memory" entitlement transfers during Disaster Recovery to the remote location.

"Xen is dead." was the way Matt introduced the section discussing Hybrid Type-1 hypervisors like Xen and Hyper-V. These run bare-metal, but require networking and storage I/O to be processed by a single bottleneck partition referred to as "Dom 0". As such, this hybrid approach does not scale well on larger multi-sock host servers. So, his Xen-is-dead message was referring to all Hybrid-based Hypervisors including Hyper-V, not just those based on Xen itself.

The new up-and-comer is "Linux KVM". Last year, in my blog post about [System x KVM solutions], I mentioned the confusion over KVM acronym used with two different meanings. Many people use KVM to refer to Keyboard-Video-Mouse switches that allow access to multiple machines. IBM has renamed these switches to Local Console Managers (LCM) and Global Console Manager (GCM). This year, the System x team have adopted the use of "Linux KVM" to refer to the second meaning, the [Kernel-based Virtual Machine] hypervisor.

Linux KVM is not a product, but an open-source project. As such, it is built into every Linux kernel. Red Hat has created two specific deliverables under the name Red Hat Enterprise Virtualization (RHEV):

• RHEV-H, a tiny ESXi-like bare-metal hypervisor that fits in 78MB, making it small enough to be on a USB stick, CD-rom or memory chip.
• RHEV-M, a vCenter-like management software to manage multiple virtual machines across multiple hosts.

Personally, I run RHEL 6.1 with KVM on my IBM laptop as my primary operating system, with a Windows XP guest image to run a few Windows-specific applications.

A complaint of the current RHEV 2.2 release from Linux fanboys is that RHEV-M requires a Windows server, and uses Windows Powershell for scripting. The next release of RHEV is likely to provide a Linux-based option for management server.

Of the various hypervisors evaluated, KVM appears to be poised to offer the best scalability for multi-socket host machines. The next release is expected to support up to 4096 threads, 64TB of RAM, and over 2000 virtual machines. Compare that to VMware Vsphere 5 that supports only 160 threads, 2TB of RAM and up to 512 virtual machines.

Linux KVM Overview

Matt also presented a session focused on Linux KVM. While IBM is the leading reseller of VMware for the x86 server platform, it has chosen Linux KVM to run all of its internal x86 Cloud Computing facilities, as it can offer 40 to 80 percent savings, based on Total Cost of Ownership (TCO).

Linux KVM can run unmodified Windows and Linux guest operating systems as guest images with less than 5 percent overhead. Since KVM is built into the Linux kernel, any certification testing automatically benefits KVM as well. KVM takes advantage of modern CPU extensions like Intel's VT and AMD's AMD-V.

For high availability, in the event that a host fails, KVM can restart the guest images on other KVM hosts. RHEV offers "prioritized restart order" which allows mision-critical images to be started before less important ones.

RHEV also provides "Virtual Desktop Infrastructure", known as VDI. This allows a lightweight client with a browser to access an OS image running on a KVM host. Matt was able to demonstrate this with Firefox browser running on his Android-based Nexus One smartphone.

RHEV also adds features that make it ideal for cloud deployments, including hot-pluggable CPU, network and storage; service Level Agreement monitoring for CPU, memory and I/O resources; storage live migrations to move the raw image files while guests are running; and a self-service user portal.

IBM has been doing server virtualization for decades. When I first started at IBM in 1986, I was doing z/OS development and testing on z/VM guest images. Later, around 1999, I started working with the "Linux on z" team, running multiple Linux images under PR/SM and z/VM. While the server virtualization solutions most people are familiar with (VMware, Hyper-V, Xen) have only been around the last five years or so, IBM has a much deeper and robust understanding and long heritage. This helps to set IBM apart from the competition when helping clients.

technorati tags: IBM, Hypervisor, PRSM, zVM, VMware, Vsphere, ESXi, VirtualBox, Parellels, Matt Archibald, Linux, KVM, RHEV, Hyper-V, RHEV-H, RHEV-M, Xen