ACM Queue - Virtualization

I/O Virtualization: Decoupling a logical device from its physical implementation offers many compelling advantages.

Mendel Rosenblum, Carl Waldspurger — Tue, 22 Nov 2011 19:27:13 GMT

The term virtual is heavily overloaded, evoking everything from virtual machines running in the cloud to avatars running across virtual worlds. Even within the narrowfigureer context of computer I/O, virtualization has a long, diverse history, exemplified by logical devices that are deliberately separate from their physical instantiations.

CTO Roundtable: Virtualization Part II: When it comes to virtualization platforms, experts say focus first on the services to be delivered.

Mache Creeger — Fri, 30 Jul 2010 16:08:40 GMT

Last month we published Part I of a CTO Roundtable forum on virtualization. Sponsored by the ACM Professions Board, the roundtable features five experts on virtualization discussing the current state of the technology and how companies can use it most effectively. In this second and final installment, the participants address key issues such as choosing the most appropriate virtual machine platform, using virtualization to streamline desktop delivery, and using virtualization as an effective disaster-recovery mechanism.

Moving to the Edge: CTO Roundtable Overview: An overview of the key issues addressed in ACM’s CTO Roundtable on network virtualization

Mache Creeger — Wed, 28 Jul 2010 16:16:52 GMT

The general IT community is just starting to digest how their world is changing with the advent of virtual machines and cloud computing. These new technologies promise to make applications more portable and raise the opportunity of more flexibility and efficiency in either on-premise or outsourced supporting infrastructure. Before taking advantage of these opportunities, however, data-center managers must have a better understanding of service infrastructure requirements than ever before. The CTO Roundtable on Network Virtualization focuses on how virtualization and clouds impact network service architectures, both in the ability to move legacy applications to more flexible and efficient virtualized environments and in what new functionality may become available. What follows are the key points of interest from that panel.

Moving to the Edge: An ACM CTO Roundtable on Network Virtualization: How will virtualization technologies affect network service architectures?

Mache Creeger — Thu, 15 Jul 2010 18:01:22 GMT

The general IT community is just beginning to digest how the advent of virtual machines and cloud computing is changing their world. These new technologies promise to make applications more portable and increase the opportunity for more flexibility and efficiency in both on-premises and outsourced support infrastructures. However, virtualization can break long-standing linkages between applications and their supporting physical devices. Before data-center managers can take advantage of these new opportunities, they must have a better understanding of service infrastructure requirements and their linkages to applications.

CTO Roundtable: Virtualization Part I: CTOs from key players in the virtualization market examine current trends in virtualization and how IT managers can make the most effective use of it.

Mache Creeger — Mon, 23 Feb 2009 08:35:42 GMT

The topic of this forum is virtualization. When investing in virtualization technologies, IT managers need to know what is considered standard practice and what is considered too leading edge and risky for near-term deployment. For this forum we've assembled several leading experts on virtualization to discuss what those best practices should be. While the participants might not always agree with each other, we hope their insights will help IT managers navigate the virtualization landscape and make informed decisions on how best to use the technology. Next month we will present part two of this forum, discussing such topics as clouds and virtualization, using virtualization to streamline desktop delivery, and how to choose appropriate virtual-machine platforms and management tools.

Network Virtualization: Breaking the Performance Barrier: Shared I/O in virtualization platforms has come a long way, but performance concerns remain.

Scot Rixner — Tue, 04 Mar 2008 08:35:34 GMT

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.

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

Ulrich Drepper — Tue, 04 Mar 2008 08:35:32 GMT

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.

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

Werner Vogels — Tue, 04 Mar 2008 08:35:30 GMT

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.

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

Tom Killalea — Tue, 04 Mar 2008 08:35:28 GMT

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.

A Conversation with Jason Hoffman: A systems scientist looks at virtualization, scalability, and Ruby on Rails.

John Stanik — Tue, 04 Mar 2008 08:35:25 GMT

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.