Data Centers

Tech Tip: Incorporate virtual servers into your DR plan

By Mike Talon

Server virtualization has begun to emerge as a hot technology in the disaster recovery arena. This technology enables you to move virtual server systems from one physical server to another with little or no reconfiguration, allowing you to seamlessly fail over to alternate hardware as needed.

Recognizing the move toward this technology, Microsoft recently acquired the Connectix product for server virtualization and rebranded it as Microsoft Virtual Server, entering a technology field that it has typically shied away from in the past. Designed to be an add-on to Windows 2003, Virtual Server allows you to create and manage multiple virtual servers on a single higher-powered machine based on the Intel chip architecture.

So far, it appears that Microsoft will only support 32-bit Windows versions. However, the software is still in the beta phase, so this is subject to change as Microsoft moves to market.

Virtualization systems that work similarly have been in use for quite some time, but Microsoft has never before lent its support to the technology. Now you can create virtual server environments that you can use without violating support contracts and otherwise limiting the help available to you if something should go awry.

Connectix Virtual PC, one of the first virtualization systems available on the market, was the driving force behind Virtual Server, and you can expect to see most of the functionality of this product passed on to its bigger brother. As with Virtual PC, Virtual Server installs on a host operating system, which in this case is Windows Server 2003.

After installing Virtual Server, you can create virtual hard disk resources that act as the disk systems for the virtual servers themselves. These can be fixed-size disks, dynamic disks that can grow as space is needed, or even virtual volumes that are bound to physical volumes in the host OS.

After creating these disk resources, you can then define your virtual servers (often referred to as guest OSs). These definitions create the virtual environment into which you install the actual operating system that the virtual server will be running. According to Microsoft, you can install all currently supported versions of Windows on a virtual server.

Since the virtual server provides virtual hardware for everything from the processor to the network cards, the hardware for every virtual server is the same, no matter what host system you're installing the environment on.

DR systems can take advantage of this technology in a variety of ways. The most apparent use is enhanced backup solutions and immediate high availability (HA) and remote availability (RA) for applications and platforms that would otherwise not support this type of DR solution. Backup enhancement with server virtualization means making backups in new ways.

In most cases, the virtual disk resource exists as a physical file on a disk, so you can back it up like any other file. This means that you can back up the entire virtual server environment without the need for bare-metal restore technologies—just the ordinary backup software. You can then restore an entire virtual server (OS, registry, applications, and data) at once and redefine the virtual server itself to completely bring the system back online in a minimum number of steps.

HA/RA solutions for certain registry-dependent applications (such as Microsoft Exchange 2000) have always posed a problem for most HA/RA tools, which essentially replicate or mirror the data well but not the system files and registry settings. With virtual server technology, you can easily replicate and/or mirror the entire server environment between host OS systems, taking all the usually nonreplicable data right along with it. Since you can define the virtual server ahead of time on the HA systems, and simply leave it offline until needed, recovery becomes a matter of just turning the virtual server on when necessary.

You can find more information at Microsoft's Virtual Server Customer Preview Web site, which contains details of the Connectix acquisition and an overview of the full feature set of the new product line.

As Microsoft brings virtualization into the mainstream, it's opening up a new world for disaster recovery—one that's been available but mostly ignored for way too long.

Mike Talon is an IT consultant and freelance journalist who has worked for both traditional businesses and dot-com startups.

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