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Challenges with adapting operating systems to virtual architectures

This tip details the challenges involved in adapting operating systems from the x86-based computing architecture to a virtualization-based computing architecture. Learn how "just enough" or JeOS slimmed-down operating systems will play into virtual appliances, Microsoft's plans for evolving with virtualization technology and why virtual machine standardization across all virtualization platforms will be important in the future.

This tip details the challenges involved in adapting operating systems from the x86-based computing architecture to a virtualization-based computing architecture. Learn: how "just enough," or JeOS, slimmed-down operating systems will play into virtual appliances, about Microsoft's plans for evolving with virtualization technology, and why virtual machine standardization across all virtualization platforms will be important in the future.

Just as virtualization has been brought forward from its mainframe beginnings, operating systems (OSes) are being and will be reincarnated in the form of hypervisors and virtual appliance software. While the changes will benefit users, the transition period could be tough; perhaps less tough for Linux than Windows. That leads us to a big question: What will Microsoft do?

In this tip, I cover the challenges posed by this major change in the IT landscape. This is the final piece of my three-part series on the impact of server virtualization on operating systems. Previously, I described how server virtualization is upending the operating system, and how server virtualization is beneficial to Linux and Unix operating systems but in some respects detrimental to the Windows Server operating system.

Several major challenges and issues must be addressed before the next generation of operating systems can achieve their full potential in a server virtualization environment. Among them are virtual appliance packaging and robustness issues, Microsoft's protective measures and standards agreements.

Packaging operating systems in virtual appliances

In order to encourage the use of virtual appliances, the server virtualization and OS vendors need to work together to develop a process for slimming down and tailoring existing operating systems to run with specific applications inside of virtual machines. By including in the virtual appliance only those portions of the operating system required to effectively support the application, vendors can reduce the footprint and security risks while increasing both efficiency and application performance.

The "JeOS" (Just Enough Operating System) concept, which has been used in developing non-virtualized software appliances, applies equally well to virtual appliances.

Some big questions remain regarding how the JeOS concept will be put into practice to build virtual appliances. For example, who will define, build and package the slimmed-down, application-tailored operating systems that run inside of a virtual appliance? Who will be responsible for supporting and maintaining them?

Linux JeOS implementations

In the case of Linux and other non-proprietary operating systems, the server virtualization and OS vendors will need to work with the application providers to provide an answer to these questions. At least two commercial operating system vendors (OSVs) are already building and supporting their own JeOS implementations: Ubuntu offers JeOS, and Red Hat provides AOS. Application providers can either look to these and other OSVs to provide the thin OS, or take on the responsibility for building, supporting and maintaining the OSes themselves.

Ideally, to help ease these tasks, a number of automated tools and processes will become available for building and packaging JeOS-style operating systems for virtual appliances. Several companies, including rPath and Novell, are already offering products that enable ISVs to combine their applications with specific, thinned-down Linux distributions to run in a virtual appliance, and then configure and maintain the software via a browser interface. And at least one non-Linux example of a JeOS exists: BEA Liquid VM, a virtualization-optimized Java Virtual Machine that is designed to enable Java applications to run directly on a virtualization layer (today, the VMware ESX Server 3 and ESX Server 3i hypervisors).

While Linux looks like an excellent candidate to be slimmed down and tailored to applications running in virtual appliances, Microsoft Windows is another story. In order for Windows to run effectively in a virtual appliance, Microsoft will either need to enable ISVs to produce a slimmed-down version, or do the job itself. In mid-2007, Microsoft signaled that it will employ both of these approaches, when it unveiled the Server Core installation option for Windows Server 2008.

Microsoft's Server Core installation option

The Server Core installation option will enable customers and ISVs to build a minimal Windows environment for specific server roles, such as Active Directory, DNS, file and print servers. Additional optional features, including failover, load balancing, and back-up, will also be supported.

Microsoft will allow administrators to remotely manage these installations via one of several common methods, such as the Microsoft Management Console (MMC) and Terminal Services Remote Desktop. The Server Core installation option is conducive to building and distributing virtual appliances, since it reduces disk footprint as well as management and maintenance requirements.

While Server Core installation is a step in the right direction, we believe that Microsoft has yet to fully articulate its plans for enabling virtual appliances. That leads to the next issue – Microsoft's virtualization roadmap and go-to-market plans.

How Microsoft will adapt to a virtualized computing environment

If the past is any guide, Microsoft will take aggressive steps to protect and continue to grow its Windows Server franchise. For one thing, Microsoft will offer its own hypervisor, Windows Server 2008 Hyper-V, within six months of the release of Windows Server 2008. Based on the news to date, customers will be able to license Hyper-V either as part of the Windows Server 2008 operating system, or as a standalone virtualization server. This will enable Microsoft to retain its control of the key layer between hardware and applications in large Microsoft accounts, but will also allow Microsoft to sell its server virtualization software to non-Windows accounts.

Microsoft's standalone Hyper-V will be bundled on major server hardware platforms, and will also be offered as a software add-on directly to corporate users for a nominal fee. Microsoft will likely offer its biggest and best customers attractive licensing and support terms to try to persuade them to standardize on Windows Server 2008 and Hyper-V across a large portion of their data centers.

Microsoft and Citrix

In addition to these product-related steps, Microsoft is working with Citrix to enable the portability of virtual machines between Windows Server 2008 Hyper-V and the Xen hypervisor in Citrix XenServer. To facilitate the interoperability between Windows and Linux platforms, Microsoft has included key virtualization-related development and packaging components, such as the hypercall API and Virtual Hard Disk Format (VHD), under the terms of its Open Specification Promise (OSP).

The OSP allows third parties to modify and implement components of Microsoft's virtualization technology without charge. In addition, Citrix is building a tool that will enable customers to more easily transfer virtual machines between Citrix XenServer and Windows Server 2008 Hyper-V. These initiatives will probably help broaden the market not just for Microsoft's virtualization offerings, but for Windows Server 2008 overall.

One thing is for certain: Microsoft will continue to take vigorous steps to protect and expand its business with enterprise customers.

Making virtual appliances ready for the enterprise

While a number of interesting, function-specific virtual appliances have recently hit the market, not too many of them have found a place in the enterprise.

Several key criteria must be met in order for virtual appliances to become enterprise-ready.

  • First, virtualization vendors must provide the infrastructure and services to enable virtual appliances to be secured and managed at an enterprise level. For example, end users would benefit from a Virtual Rights Management (VRM) interface in a VMware environment, to enable IT security administrators to set up and implement policies to regulate network-based user access of virtual appliance services, as well as secure enterprise data through authentication, encryption and copy protection controls. Enterprise users will also require easy-to-use patching mechanisms for virtual appliance software, along with other lifecycle management services.

  • Second, both ISVs and end users must be given the ability to build and custom-configure each virtual appliance to include just the set of features and services required. A simple-to-use authoring system would encourage vendors and users to deploy virtual appliances for a whole variety of function-specific services.

  • Finally, virtual appliances should be certified against a common industry standard, to ensure that enterprise customers can know and trust what they are getting from appliance vendors. VMware's certification program is a good start, as it ensures both that customers will get a great "out-of-the-box" experience and that the vendor will support the entire software stack – including OS and middleware – running in the virtual appliance. The next step is for the virtualization vendors to work toward a common, baseline certification standard, which will help pave the way for widespread adoption.

Virtual machine standardization

One of the most critical issues from an end user's perspective is whether the industry will adopt standards that will enable a virtual machine, regardless of its origin, to run on any major hypervisor platform. This would provide end users with the freedom to "hire" and "fire" their server virtualization vendor, or even mix and match vendors and platforms for particular projects, while still protecting their existing virtualization investments. This, in turn, should lead to vigorous competition at each layer of the stack, including at least three major hypervisors plus a broad range of operating systems adapted to run in virtual appliances.

Competition will strongly motivate both server virtualization and OS vendors to reduce the prices of their offerings over time, in order to grow or at least maintain market share. These pricing reductions will not only benefit end users, but also help to accelerate the growth of the server virtualization customer base. Robust competition will also help to increase the rate of innovation in both server virtualization and operating system products. End users clearly win on both counts.

Server operating systems will survive

The tremendous growth in server virtualization is leading to a transformation, both in the way computing gets done, and in the segmentation of the x86 software stack that has helped to define the industry landscape for more than 30 years. In the midst of this transformation, the operating system is being re-invented, as its key functionality is bifurcated into the hypervisor and virtual appliance layers of the new software stack.

While this new approach has the potential to benefit end users and application providers in a big way, a number of significant challenges must be overcome before these benefits can be realized. Though the transition to server virtualization will be difficult, and even painful, for some participants, we are confident that the major industry players will work through the issues and, in the end, do the right thing for their end customers.

Jeff Byrne is a senior analyst and consultant at Taneja Group, where he focuses primarily on the server virtualization market. Prior to joining Taneja Group, Jeff spent more than five years at VMware as vice president of marketing and later vice president of corporate strategy. Jeff's past experience includes marketing leadership roles at companies such as MIPS, HP and Novell.

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