Virtualization

Vol. 6 No. 1 – January/February 2008

Virtualization

Articles

Network Virtualization: Breaking the Performance Barrier

The recent resurgence in popularity of virtualization has led to its use in a growing number of contexts, many of which require high-performance networking. Consider server consolidation, for example. The efficiency of network virtualization directly impacts the number of network servers that can effectively be consolidated onto a single physical machine. Unfortunately, modern network virtualization techniques incur significant overhead, which limits the achievable network performance. We need new network virtualization techniques to realize the full benefits of virtualization in network-intensive domains.

Network Virtualization: Breaking the Performance Barrier

Shared I/O in virtualization platforms has come a long way, but performance concerns remain.


Scott Rixner, Rice University


The recent resurgence in popularity of virtualization has led to its use in a growing number of contexts, many of which require high-performance networking. Consider server consolidation, for example. The efficiency of network virtualization directly impacts the number of network servers that can effectively be consolidated onto a single physical machine. Unfortunately, modern network virtualization techniques incur significant overhead, which limits the achievable network performance. We need new network virtualization techniques to realize the full benefits of virtualization in network-intensive domains.

To share a network interface among a set of virtual machines, the VMM (virtual machine monitor) must accomplish two key tasks. First, the VMM must provide shared access to the network interface. This means that the virtual machines’ outgoing network traffic must be multiplexed together before being sent over the network; similarly, incoming network traffic must be demultiplexed before being delivered to the appropriate virtual machines. Second, the VMM must protect the virtual machines from each other. This means that no virtual machine can be allowed to transfer data into or out of another virtual machine’s memory. Therefore, the challenge in network virtualization is to provide efficient, shared, and protected access to the network interface.

by Scot Rixner

Interviews

A Conversation with Jason Hoffman

Jason Hoffman has a Ph.D. in molecular pathology, but to him the transition between the biological sciences and his current role as CTO of Joyent was completely natural: "Fundamentally, what I've always been is a systems scientist, meaning that whether I was studying metabolism or diseases of metabolism or cancer or computer systems or anything else, a system is a system," says Hoffman. He draws on this broad systems background in the work he does at Joyent providing scalable infrastructure for Web applications. Joyent's cloud-computing infrastructure has become the foundation for many of the increasingly popular applications developed to feed into the social-networking site Facebook.com.

A Conversation with Jason Hoffman

A systems scientist looks at virtualization, scalability, and Ruby on Rails

Jason Hoffman has a Ph.D. in molecular pathology, but to him the transition between the biological sciences and his current role as CTO of Joyent was completely natural: “Fundamentally, what I’ve always been is a systems scientist, meaning that whether I was studying metabolism or diseases of metabolism or cancer or computer systems or anything else, a system is a system,” says Hoffman. He draws on this broad systems background in the work he does at Joyent providing scalable infrastructure for Web applications. Joyent’s “cloud-computing” infrastructure has become the foundation for many of the increasingly popular applications developed to feed into the social-networking site Facebook.com.

In our discussion with him this month, Hoffman discusses some of the key technologies behind that infrastructure. Among these technologies is virtualization, which we explore in-depth in the four feature articles that make up this month’s Queue Focus. Hoffman also shares his insight on the popularity of Ruby on Rails, a technology he has been involved with since its inception and about which he is frequently asked to speak at conferences.

Articles

Beyond Server Consolidation

Virtualization technology was developed in the late 1960s to make more efficient use of hardware. Hardware was expensive, and there was not that much available.

Beyond Server Consolidation

Server consolidation helps companies improve resource utilization, but virtualization can help in other ways, too.

WERNER VOGELS, AMAZON.COM

Virtualization technology was developed in the late 1960s to make more efficient use of hardware. Hardware was expensive, and there was not that much available. Processing was largely outsourced to the few places that did have computers. On a single IBM System/360, one could run in parallel several environments that maintained full isolation and gave each of its customers the illusion of owning the hardware.1 Virtualization was time sharing implemented at a coarse-grained level, and isolation was the key achievement of the technology. It also provided the ability to manage resources efficiently, as they would be assigned to virtual machines such that deadlines could be met and a certain quality of service could be achieved.

At first glance it appears that not much has changed. Today the main application of virtualization technology in the enterprise is to combat server sprawl through virtualization-based consolidation. Isolation, security, and efficiency remain the main benefits of using virtual machines in this context.

by Werner Vogels

How OSGi Changed My Life

In the early 1980s I discovered OOP (object-oriented programming) and fell in love with it, head over heels. As usual, this kind of love meant convincing management to invest in this new technology, and most important of all, send me to cool conferences. So I pitched the technology to my manager. I sketched him the rosy future, how one day we would create applications from ready-made classes. We would get those classes from a repository, put them together, and voila, a new application would be born.

How OSGi Changed My Life

The promises of the Lego hypothesis have yet to materialize fully, but they remain a goal worth pursuing.

PETER KRIENS, AQUTE

In the early 1980s I discovered OOP (object-oriented programming) and fell in love with it, head over heels. As usual, this kind of love meant convincing management to invest in this new technology, and most important of all, send me to cool conferences. So I pitched the technology to my manager. I sketched him the rosy future, how one day we would create applications from ready-made classes. We would get those classes from a repository, put them together, and voila, a new application would be born.

Today we take objects more or less for granted, but if I am honest, the pitch I gave to my manager in 1985 never really materialized. The reuse of objects never achieved the levels foreseen by people such as Brad Cox with his software-IC model, and many others, including myself. Still, this Lego hypothesis remains a grail worth pursuing.

by Peter Kriens

Meet the Virts

When you dig into the details of supposedly overnight success stories, you frequently discover that they've actually been years in the making. Virtualization has been around for more than 30 years since the days when some of you were feeding stacks of punch cards into very physical machines yet in 2007 it tipped. VMware was the IPO sensation of the year; in November 2007 no fewer than four major operating system vendors (Microsoft, Oracle, Red Hat, and Sun) announced significant new virtualization capabilities; and among fashionable technologists it seems virtual has become the new black.

Meet the Virts

Virtualization technology isn’t new, but it has matured a lot over the past 30 years.

TOM KILLALEA, AMAZON.COM

When you dig into the details of supposedly “overnight” success stories, you frequently discover that they’ve actually been years in the making. Virtualization has been around for more than 30 years—since the days when some of you were feeding stacks of punch cards into very physical machines—yet in 2007 it “tipped.” VMware was the IPO sensation of the year; in November 2007 no fewer than four major operating system vendors (Microsoft, Oracle, Red Hat, and Sun) announced significant new virtualization capabilities; and among fashionable technologists it seems virtual has become the new black.

What is it?

Virtualization is the provision of an abstraction between a user and a physical resource in a way that preserves for the user the illusion that he or she could actually be interacting directly with the physical resource. While you could imagine virtualizing any physical resource, the focus of this issue of Queue is the computing machine virtualization that is the current rage. The user gets a high-fidelity copy of what appears to be a complete computer system, while he or she is actually dealing with an abstraction layer known as the VMM (virtual machine monitor) that runs on the real machine and maps resources on behalf of the user.

by Tom Killalea

Kode Vicious

Poisonous Programmers

Dear KV, I hope you don't mind if I ask you about a non-work-related problem, though I guess if you do mind you just won't answer. I work on an open source project when I have the time, and we have some annoying nontechnical problems. The problems are really people, and I think you know the ones I mean: people who constantly fight with other members of the project over what seem to be the most trivial points, or who contribute very little to the project but seem to require a huge amount of help for their particular needs. I find myself thinking it would be nice if such people just went away, but I don't think starting a flame war on our mailing lists over these things would really help. Any thoughts on this nontechnical problem?

Poisonous Programmers

A koder with attitude, KV answers your questions. Miss Manners he ain’t.

It’s well known that the success or failure of projects depends just as much on having the right people as it does on technology. But how do you prevent certain “rogue elements” from sabotaging your project? KV has lots to say about this “nontechnical problem.” And surprise! His solution involves neither physical nor verbal abuse. We encourage you to suggest your own solution, or ponder other problems, in e-mails to kv@acmqueue.com.

by George Neville-Neil

Articles

The Cost of Virtualization

Virtualization can be implemented in many different ways. It can be done with and without hardware support. The virtualized operating system can be expected to be changed in preparation for virtualization, or it can be expected to work unchanged. Regardless, software developers must strive to meet the three goals of virtualization spelled out by Gerald Popek and Robert Goldberg: fidelity, performance, and safety.

The Cost of Virtualization

Software developers need to be aware of the compromises they face when using virtualization technology.

ULRICH DREPPER, RED HAT

Virtualization can be implemented in many different ways. It can be done with and without hardware support. The virtualized operating system can be expected to be changed in preparation for virtualization, or it can be expected to work unchanged. Regardless, software developers must strive to meet the three goals of virtualization spelled out by Gerald Popek and Robert Goldberg: fidelity, performance, and safety.1

We may make compromises for each of the goals. For example, people in some situations are OK with sacrificing some performance. In fact, this is almost always mandatory for performance: compared with execution of an operating system on naked hardware, execution of a virtualized operating system takes more effort and somehow must be paid for.

by Ulrich Drepper

Curmudgeon

All Things Being Equal?

By the time these belles-lettres reach you, a brand new year will be upon us. Another Year! Another Mighty Blow! as Tennyson thundered. Or as Humphrey Lyttelton (q.g.) might say, "The odious odometer of Time has clicked up another ratchette of entropic torture." Less fancifully, as well as trying hard not to write 2007 on our checks, many of us will take the opportunity to reflect on all the daft things we did last year and resolve not to do them no more. Not to mention all the nice things we failed to do. I have in mind the times when I missed an essential semicolon, balanced by the occasions when inserting a spurious one was equally calamitous. Surely any half-decent computer language should know where my statements are meant to terminate, and then properly redistribute the punctuation provided? The smarter Lisps became good at DWIM (do what I mean), balancing those damned, spurious parentheses. But I digress, having planted a topic known to incite reader feedback.

All Things Being Equal?

New year, another perspective

Stan Kelly-Bootle, Author

By the time these belles-lettres reach you, a brand new year will be upon us. “Another Year! Another Mighty Blow!” as Tennyson thundered. Or as Humphrey Lyttelton (q.g.)1 might say, “The odious odometer of Time has clicked up another ratchette of entropic torture.” Less fancifully, as well as trying hard not to write 2007 on our checks, many of us will take the opportunity to reflect on all the daft things we did last year and resolve not to do them no more.2 Not to mention all the nice things we failed to do. I have in mind the times when I missed an essential semicolon, balanced by the occasions when inserting a spurious one was equally calamitous. Surely any half-decent computer language should know where my statements are meant to terminate, and then properly redistribute the punctuation provided? The smarter Lisps became good at DWIM (do what I mean), balancing those damned, spurious parentheses. But I digress, having planted a topic known to incite reader feedback.3

As one of our Anglican General Confessions humbly confesses, “We have left undone those things which we ought to have done. And we have done those things which we ought not to have done.” One is never sure if all denominations still use the exact wording acquired from youthful, schooled repetition of Daily Morning service. That sonorous balance of sinful omission and commission has probably been diluted in some LaxLib parishes: “O Lord, considering my genes, nasty parents, and an inadequate educational system, I haven’t done that badly.” That’s not quite as cynical as you might think. I find that what we used to confess as “There is no good in us” has been changed in some services as “There is no health in us.”

by Stan Kelly-Bootle

Interviews

The Ever Expanding Ecosystem for Embedded Computing

Mike Vizard from ACM Queue talks with Oracle's Mike Olson about the changing architecture of network-enabled applications. Olson explains the thinking behind the company's new focus on embedded database and middleware technology. He explores the technical, business and economic forces shaping this fast-growing market. Tune in to learn how Oracle plans to serve customers way outside the enterprise.

Mike Vizard from ACM Queue talks with Oracle's Mike Olson about the changing architecture of network-enabled applications. Olson explains the thinking behind the company's new focus on embedded database and middleware technology. He explores the technical, business and economic forces shaping this fast-growing market. Tune in to learn how Oracle plans to serve customers way outside the enterprise.