Virtual appliances and the changing role of operating systems

Summary:VMware co-founder Mendel Rosenblum gives me a tutorial on virtualization and the coming age of virtual appliances, which are changing the role of operating systems. With virtual appliances, an OS just needs to provide interfaces for the applications running on top of it. As a result, OSs will get smaller and thinner, and applications more reliable and easier to manage.

A few months ago I found myself waiting for a flight at the Burbank airport with Mendel Rosenblum. He is a co-founder of VMware and chief scientist at the company and an assistant professor in the Department of Computer Science at Stanford.

VMware was founded in 1998 by Rosenblum and his wife, Diane Greene (who is CEO of the company), and  three other engineers. The was sold to EMC in January 2004 for $635 million in cash.

Rosenblum gave me a tutorial on virtualization and the coming age of virtual appliances. Subsequently, I saw a presentation by Srinivas Krishnamurti, VMware director of product management, on virtual appliances and how the concept is gradually changing how operating systems are conceived, which brought me back to my earlier conversation with Rosenblum. We talked about the latest trends in virtualization, which along with Web services and reducing power consumption is changing the economics of datacenters.

I asked Rosenblum what he thought were major misconceptions about virtualization.“The biggest misconception is server consolidation. It was the first big application in the enterprise. Part of the problem with being the first successful application is that it misses a lot of the benefits. A virtualization layer is a different way of thinking about hardware, and server consolidation is just one tiny sliver of it,” he said.

“People deploying virtualization infrastructure now view hardware differently--you have a pool of resources, virtual machine units, and you allow the infrastructure to map onto computation. If you need more capacity, just add more hardware.”

“The other aspect is using hardware more efficiently. The TCO is straightforward, but the real value you get is to think about capability to manage software much better. The value proposition is clear--capitalize on delivering software services. Virtualization was hot in the 1970s on the mainframe and it is coming back today on commodity computing  platforms mainly because you have a better way to manage services running on virtual machine. You think about exporting services, as logical units, operating on at a higher level.”

Rosenblum continued, “It’s just a better way to think about a datacenter. It allows you to operate at a level of what services rather than the components—each motherboard, what OS, how much memory. You don’t need to worry about the OS, just what services. It’s the level of automation that counts. This sort of vision has gone under a lot of names, such as autonomic [IBM’s term] or utility computing.”

The role of the OS in a virtual appliance becomes more about supporting applications. “In Windows and Linux, for example, the applications are coded to those APIs. Over time, there could be operating systems targeting different kinds of applications,” Rosenblum said. “Effectively if you look at reliability and security, you want to simplify, have an environment where can lop off everything not being used. When people start deploying OSs this way, such as for SAP or Oracle applications, you just want to have an OS that delivers what you need. With Linux and Windows you get the whole thing.”

Krishnamurti defined a virtual appliance as a preinstalled and preconfigured application packaged along with an OS in a virtual machine. “The role of an OS is changed. It just needs the interfaces for the applications running on top of it. As a result, OSs will get smaller and thinner. You pick an OS, fine tune it and package it up, and you don’t have to install fixes if they are not applicable. You could build an OS for supporting java virtual machines, and the customer wouldn’t know the difference, but it would be more secure and reliable.”  

Krishnamurti cited the benefits of virtual appliances as smaller download sizes, simpler test matrices for Q&A, easier to manage and potentially less surface area vulnerable to attack.

About 300 virtual appliances run on top of VMware's platform to date, Krishnamurti said, including Red Hat, Novell, Ubuntu and rPath on the OS front.

rPath is targeting virtual appliances and what it calls "software appliances," which combine an application and a streamlined OS that runs on industry-standard hardware.  rPath just announced support for creating virtual appliances that run on the Xen 3.0.3 hypervisor with rPath’s rBuilder.

According to Brett Adam, vice president of product development, rPath takes a standard Linux distribution and repackages it so all dependencies between the pieces are clear, and then provides only the pieces required for an application.  Adam said rPath has about 1,000 active appliance projects.

Zimbra is trying to reduce size of its Linux variant by up to one gigabyte, taking it down to half a gigabyte in size, according to John Robb, vice president of marketing and product management. 

Operating system companies--Microsoft and Red Hat--have tried to fight virtualization, Krishnamurti said, but now they want to keep control of virtualization layer, keeping their fingers on the hardware. “It going to be an interesting time for what system software gets supported going forward in next couple years,” Krishnamurti said.

Rosenblum doesn't expect to see new OSs popping up any time soon, however.“New operating systems are further out. We see some demand, but there are entrenched behaviors,” Mendel said. “OS research has gotten depressed over the years—there are only two major OSs. The core abstraction of OSs have solidified so much that it hasn’t left a lot of room for innovation.”

I asked Rosenblum if he had any interest in starting up another software company. "If I did another company, an OS builder is what I would tackle,” he said. That sounds like an emerging computer science and business opportunity in his wheelhouse...

Topics: Virtualization

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