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Virtualization Workloads, a comparative study in Open Source environments

August 7, 2008 by Kris Buytaert Leave a Comment

At the Ottawa Linux Symposium, Benoit de Lingeris and his team from Revolution Linux presented their paper “Virtualization of Linux Server, a comparative study“, mostly the work of Fernando L. Camargos in pursuit of his Masters degree in Computer Science.

They looked at VirtualBox, Xen, KVM, OpenVZ, LinuxVServer and KQemu in an 64bit mode for all tests where possible (hence not for VirtualBox). Their Host OS was Ubuntu 7.10 and the VM’s were Ubuntu 6.06.

It’s pretty obvious that virtualization creates a little overhead, the bigger question however is how much overhead? What’s the penalty when virtualizing an environment? They focused on several aspects, the first one was just trying to figure out what impact the addition of a hypervisor had on an environment.
The second one how many virtual machines one could run in a virtualized environment.

They ran their tests multiple times and the results presented where averages of these tests.

In the first set of tests, impact of the hypervisor compared to the real native machine, they started of with a Linux Kernel compilation workload.

Here Linux Vserver lost almost no performance closely followed by Xen and then OpenVZ. Compared to native machine speed Both VirtualBox and (K)Qemu scored below 50%.
Their second test was file compressions. Here most of the environments scored around 85-95% native speed except from KQemu and OpenVZ.

The Samba team brought us dbench, “dbench is a filesystem benchmark that generates load patterns similar to those of the commercial Netbench benchmark, but without requiring a lab of Windows load generators to run. It is now considered a de-facto standard for generating load on the Linux VFS.”
Here LinuxVserver outscales the rest , Linux VServer scores good here as they use directly the IO drivers of the system where as others don’t. Xen is second best in this test but the other frameworks really need some work done here.

If you want to do low level data copy on UNIX obviously dd is your favorite tool. For the same reasons as above Linux-Vserver scores good here. The strange thing however is that it scores better than Native speed. When copying an existing file Xen and KVM are a good second but OpenVZ seemed to need some work. Another interesting fact is that KQemu and VirtualBox failed the test. When copying data from /dev/zero KVM scores better.

During the test the block devices were backed by different technologies , for Vserver it was a native disk , for Xen a file. Off course this doesn’t give equally good results. Different options for tuning are available here. Still a good advise, do not virtualize your fileserver.

When looking at network IO performance the team opted to use netperf for the test. VirtualBox, Linux-Vserver, Xen and OpenVZ all score good here. The performance of KQemu and KVM were a disaster.
When testing an Rsync with different filesizes OpenVZ scored best and most of the other tools performed around 80% native machine speed , except for KVM that seemed to have more problems with 1 big file than with different small ones. The good scores of VirtualBox are because of their modified IP stack and their efforts there obviously were worth the time…

So they covered, compiling, disk IO, network IO, obviously we want to know a bit about Database performance too. Revolution Linux chose Sysbench for this test. Again good scores for Linux-Vserver and xen , less for the rest

With strange Looks from the OpenVZ people in the audience they concluded that Linux-Vserver has excellent performance and has presented minimal overhead , off course Linux-VServer and OpenVZ are still chroots on steroids, not full virtualization solution. According to Revolution Linux Xen achieved great performance in most of the tests. KVM was fairly good for full virtualization but didn’t perform well for applications relying on I/0

As mentioned earlier apart from the overhead tests Revolution Linux also set to test the scalability , Only 2 tests here kernel compilation and Sysbench performed with n ( n = 1 , 2, 4,8 ,16 and 32) instances .

If they looked at the Number of Transactions globally per host , so spread over the different Virtual Machines) Xen is the best perform it actually reached a higher total throughout with 32 virtual machines than wit 1 vm, peaking at 4-8 VM’s.

With their new benchmark Kernels Compiled per hour , they only have results for Vserver and Xen. With 1 VM both VServer build around 10-11 Kernels per hour , and as of 2/4 VM’s they go up to 20. Xen keeps pace up to 16 VM’s and then slows down.

So obviously there is a very strong correlation between the performance of a machine and the number of instances in that machine.
Also here Linux-Vserver scores better than average with Xen as a good alternative for bare metal Virtualization.

Their conclusions: It has to be said that Revolution Linux is a Linux-VServer shop , and that’s where their preference goes. If they have to be able to run different kernels they seem to prefer Xen.

Generally speaking it seems lots of optimization could be done for different setups. often other than the default setups could help a technology gain a significant boost in performance.

Different network setups ,using specific network stacks ,
or different disk backends (real disk vs file based backends) a lot can change with tuning and installation by experience people.
The tests also have been performed about 6 months ago .. which means that today the results might probably be a lot different.

Filed Under: Guest Posts, News Tagged With: kvm, linuxvserver, ols, openvz, Ottawa Linux Symposium, revolutionlinux, ubuntu, VirtualBox, virtualization, workload, Xen

Rich Wolski on Eucalyptus: Open Source Cloud Computing (Video Interview – 2/2)

July 18, 2008 by Toon Vanagt Leave a Comment

In this second part of our video interview with Rich Wolski (see the first part here), recorded at the O’Reilly Velocity conference, we learn how Eucalyptus came around the Amazon subscription method, where credit cards are the key to authentication. Offering ‘free and open’ clouds in university environments was achieved by introducing a system administrator in between the user account request and the issuing of certificates. Upon user request, the Eucalyptus user subscription interface generates an e-mail to an administrator, who will then perform a ‘manual’ verification. This can be a phone call or a physical meeting.


Eucalyptus Director Rich Wolski on open source cloud computing, Xen and Amazon’s EC2 (part 2/2) from Toon Vanagt on Vimeo.

Users did not like Rocks (leading open source cloud management tool), but the community (in smaller community/ deployment supports) preferred to do this manually. So Eucalyptus 1.1 provides Guidance, a script to build from scratch by hand.

A ‘build with one button’ remains the goal for future versions.

The full Eucalyptus image is only 55 Mb (without Linux image) and includes the necessary packages in order to make sure all of the revision-levels are fully compatible. Eucalyptus comes as Free BSD Open-Source license with a small disclaimer that the University of Santa Barbara explicitly wants to avoid any intellectual property infringements and will take necessary steps if needed.

Virtualization is supported by Xen 3.1 for security sake (3.0 works too, but is discouraged).

Lessons learned in building clouds from open source are quite rare. Here are a few from Rich:

Unlike commercial environments (where one controls the configuration, hardware purchase and networking), the architectural decisions are very different in open source environment, where one does not know the installation. One of the current challenges is to build a system depending on the control you have over your specific installation, you could successfully remove more of the portability from the system as you needs fit.

A second lesson is that people do things by hand and this is an opportunity for automation. Nobody is deploying Linux manually, instead sys admin use distributions. Shouldn’t there be a similar cloud distribution product out there? The people at Puppet were eager to help on providing such scripts for cloud deployments. According to Rich, this illustrates how O’Reilly should be credited for creating a good atmosphere at the Velocity 08 conference where a lot of cross-fertilization happened.

Rich ends the interview by throwing a fundamental question at the cloud community. He classifies current cloud initiatives on a scale based on the ‘closeness’ of the application layer to the cloud API. At the one end of this spectrum, he puts Google Apps (with Python oriented function calls) and at the other end Amazon EC2 (a set of very simple web service interfaces to the underlying virtualization technology) and all other cloud offerings float in between. This impacts what you can do with virtualization. Google AppEngine becomes your compiler on their end of the scale.

Rich wonders if this tighter link to the Google AppEngine will become a liability or an asset in the future when it comes to virtualization capabilities?

We invite you to provide your answers in the comments below!

Filed Under: Interviews, People, Videos Tagged With: Amazon EC2, cloud computing, ec2, eucalyptus, interview, kvm, LibVert, O'Reilly, O'Reilly Velocity, open source, open source cloud computing, Rich Wolski, VDE, video, video interview, virtualisation, virtualization, vmware, Xen, Xen virtualization

New Linux Kernel: More Support for Virtualization

July 16, 2008 by Robin Wauters Leave a Comment

Nearly three months in the making, the new Linux kernel (version 2.6.26) announced by Linus Torvalds through a mailing list, boasts read-only bind mounts, “big-iron” KVM ports, USB webcam support, 802.11s mesh WiFi, built-in support for remote kernel debugging, and a host of embedded architecture improvements, among other enhancements.

Among the most significant improvements are changes to the Kernel-based Virtual Machine (KVM) virtualization software, first included in the kernel in February of last year. KVM normally uses the technique of full virtualization, which simulates all the underlying hardware necessary to run a given client system, with the support of virtualization technologies built into AMD and Intel chips. The latest kernel update adds limited support for paravirtualization, a technique that only partially virtualizes the hardware in order to improve performance.

KVM has also, for the first time, been ported to non-x86 hardware platforms Intel IA64 and IBM PPC and S/390, developers said.

[Source: ZDNet UK]

Filed Under: News Tagged With: kernel, kernel 2.6.26, Kernel-based Virtual Machine, kvm, Linus Torvalds, linux, linux kernel, Linux kernel 2.6.26, paravirtualization, virtualisation, virtualization

Rich Wolski on Eucalyptus: Open Source Cloud Computing (Video Interview – 1/2)

July 8, 2008 by Toon Vanagt 4 Comments

A month ago we reported on how you can build your own open source cloud on clusters to make your personal cloud dreams come true!  Simply put your datacenter to use by ordering Xen virtualization on the Rocks and then carefully roll it in fresh Eucalyptus leaves.

In order to learn what makes these clouds tick, we have sent our enthusiastic cloud computing koala Toon Vanagt to San Francisco to interview Eucalyptus Director Rich Wolski at the O’Reilly Velocity conference. Below, you can find the first part of this exclusive video interview (we’ll post the second part tomorrow).

Rich’s students came up with EUCALYPTUS, which stands for ‘Elastic Utility Computing Architecture for Linking Your Programs To Useful Systems’ as an open-source tool for doing “cloud computing”. Their tool is designed to stimulate the development, interest, experiments and research into the nascent concept and industry of cloud computing.

Eucalyptus was build in a modular fashion, so it can “mimic” the interface of popular commercial clouds, like the one they started off with, Amazon EC2. The team plans support for several cloud interfaces as long as they are public and well documented.

Rich underlined that Eucalyptus is designed to experiment and not to compete with industrial strength clouds as Amazon EC2. Although with some engineering, one could take parts of Eucalyptus, mature those and scale to specific needs.

When asked about the underlying virtualization experience, Xen is seen as a very useful technology in ‘cloud’ regards. Rich complements Xen on being well documented and conceptually easy to understand and he looks back at the Xen selection as a good first hypervisor choice. Due to the nature of their specific use, parts of Xen would ‘break’ under load and were modified to meet certain stability needs.

As LibVert is used, Eucalyptus should in theory be relatively easy be able to support other hypervisors such as VMware and KVM. If no major wrinkles appear on the development surface, Eucalyptus therefore expects to support VMware and KVM with its 2.0 release, scheduled for early September 2008.

Rich supportively points to the Enomalism elastic computing platform, an open source cloud platform that enables a scalable enterprise IT and local cloud infrastructure. as an alternative open source virtualization system.

Security remains an issue but in some respects, accountability and authentication are an even bigger problem to the open source community than within commercial projects. “In an academic space, where you are not paying for usage, it is not a credit card that you are accounting to, but a user”. So Eucalyptus had to devise a user accounting system that is based on certificates. On top of that components should not be ‘spoofable’, as there is no message encryption in Eucalyptus (yet). Because these messages can be spoofed, Rich’s team had to take care of an open source implementation of Web Services Security to make sure the cloud controllers cannot be ‘fooled’ by malicious messages of doubtful origin.

The shortage of public IP addresses in university environments was solved by using the open source technology VDE (Virtual Distributed Ethernet). [VDE is an ethernet compliant virtual network that can be spawned over a set of physical computer over the Internet. You can see VDE as the software incarnation of a hardware network switch plus attached cables. Using the vde_switch and vde_plug programs you are able to create quite complex virtual analogies of a network that can span several hosts, even across the Internet.

By creating a virtual Ethernet for every cluster allocation and make that a set of user space processes can tunnel through NATs (Network Address Translation). As a downside to this VDE implementation comes a performance penalty. So Eucaluptus is offered with 2 flavors, linked to the SLA-nature in cloud computing. The first option uses the described very flexible ‘Virtual VLAN’ independent of IP-addresses. The second option bypasses VDE and is faster but less scalable as limits user requests to the confines of a single cluster.

Tomorrow, we’ll publish the second part of this exclusive interview. Stay tuned!

Filed Under: Interviews, People, Videos Tagged With: Amazon EC2, cloud computing, ec2, eucalyptus, interview, kvm, LibVert, O'Reilly, O'Reilly Velocity, open source, open source cloud computing, Rich Wolski, VDE, video, video interview, virtualisation, virtualization, vmware, Xen, Xen virtualization

Red Hat Unveils Virtualization Strategy At Boston Summit

June 19, 2008 by Robin Wauters 2 Comments

Today at Red Hat Summit in Boston, two of Red Hat’s emerging technology engineers, Dan Barrange and Richard Jones, presented the new tool sets that their team has developed for work with Xen virtual machines (VMs). It includes command line utilities, which will become part of the oVirt tool set, a web-based virtual machine management console built using Ruby on Rails.

oVirt uses Red Hat’s open source libvirt management framework that provides hypervisor-agnostic management interfacing, allowing the same tools to manage multiple different hypervisors. Libvirt already supports six hypervisors : Xen, KVM, QEMU, OpenVZ, Linux Containers (LVX) and Solaris LDoms.

The company also announced that its own embedded, lightweight, stand-alone hypervisor and accompanying management console are available in beta right now. Red Hat’s new Linux hypervisor hosts both Red Hat Enterprise Linux and Microsoft Windows operating systems. Rather than base the software on the open-source Xen hypervisor, Red Hat has chosen the KVM (Kernel-based Virtual Machine) project, which is already used by the major Linux OSs as the default server virtualization package. Another key difference: while Xen works well with Linux, it’s an add-on. KVM, on the other hand, is an integral part of Linux.

Read more about Red Hat’s virtualization announcements here.

Filed Under: Featured, News Tagged With: Hypervisor, kvm, linux, management console, oVirt, qumranet, red hat, Red Hat Bostom Summit, Red Hat Enterprise Linux, Red Hat hypervisor, Red Hat Summit, virtualisation, virtualization, virtualization management console, Xen

KVM vs Xen, Who Will Win The Fight?

May 9, 2008 by Kris Buytaert Leave a Comment

Ian Pratt and Benny Schnaider are using strong words against each other.

As KVM is gaining more and more popularity by being adopted in several Linux distributions, including Ubuntu, the battle between different virtualization technologies continues to be interesting.

While KVM is being adopted by a variety of software and distribution vendors, Xen is being adopted by hardware vendors to be shipped directly with the iron.

We asked Ian at FOSDEM if he felth the Xen community was changing and if he thought the contributions from the community were slowing down.

“We certainly haven’t seen that. If you think about the life of the Xen project, there have been a number of significant changes. When we left the University to set up XenSource, people were worried we might go off and take Xen in closed source or something, but we didn’t. One of the things that we did do was just to provide greater transparency by setting up the Xen advisory board and the Xen.org website. The advisory board has members from companies like Intel, AMD, HP, IBM, … big companies that are now contributing to Xen and have oversight from the advisory board, so I think the community is pretty happy and it’s going from strength to strength.”

According to ZDNet, Ian also claims that “KVM is not a true hypervisor. It tries to add virtualization capabilities to the Linux kernel but it’s not a true hypervisor approach. The Xen community is alive and well. Xen is a true hypervisor architecture that’s better for scalability, security and availability.

One of the biggest arguments against Xen is that KVM is already in the kernel. Theodore Ts’o thinks “it’s inevitable that Red Hat and Novell will standardize on KVM because of its inclusion in the kernel.” Xen never finished their efforts and KVM was quickly adopted into that same Linux Kernel.

Strong words also from the KVM front:

“If Xen will die or not die, I don’t know. But KVM will take over and be the virtualization selection of choice,” said Benny Schnaider, CEO and co-founder of Qumranet.

KVM or Xen? Time will tell, today both have different features and it will take some time until their feature set is similar, so the choice is about what YOU need, not about what the vendors claim you need.

[Source: ZDNet]

Filed Under: People Tagged With: benny schnaider, Ian Pratt, kvm, qumranet, ted tso, Xen, xensource

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