Virtualization Options

Virtualization is a major buzzword, but which virtualization platform meets your specific needs? In general you can divide the different offerings into four sections:

Server Virtualization

Server virtualization enables corporate, and private users, to consolidate servers, run legacy OSs and applications. The main benefits are reduced power consumption by reducing the amount of physical servers in the datacenter, faster server deployment, better hardware utilization and better scalability. The main contenders in the Server Virtualization field are:

• VMware Server
• VMware Virtual Infratstructure (ESX)
• Microsoft Virtual Server 2005
• SWsoft Virtouzzo
• Xen

All but one of these has one thing in common, they all add a hardware virtualization layer on top of an existing OS like Windows Server 2003 and Linux, which means that you have to first install the base OS, then add the virtualization layer. VMware ESX server is different though, as that installs directly on the bare-metal hardware without the need for a base host OS. This gives ESX Server a definitive edge as the specialized light-weight kernel it provides boosts VM performance and combined with the VirtualCenter management software lets you easily shuffle your VMs around between several ESX based hosts for optimal performance and no-downtime hardware maintenance. ESX server offers the best performance and scalability, but it does come at a price both licensing wise and infrastructure wise. Because of ESX Server's lightweight kernel, it has significantly less overhead and provides much better performance than VMware Server or Virtual Server 2005. To utilize all the features it provides you definitely need some kind of shared storage like Fibre Channel, iSCSI, NAS or NFS and if you want to run it in a production environment you need to make sure that all your hardware is listed on the VMware HCL (Hardware Compatibility List) which is constantly updated. While ESX comes with a somewhat hefty price tag, VMware Server, Microsoft Virtual Server 2005 and Xen 3.0 represents the other side of the cost scale. They are all available for free, and can be a quick and easy way to get started with server Virtualization. As for SWsoft's Virtouzzo, I'm not sure how that compares pricing wise, as I've never seen specific pricing of that product. Comparing a true hypervisor solution like ESX Server to the othee products is really comparing apples to oranges As of today, VMware ESX Server is unrivaled in the x86 Server Virtualization field. No other product offers the same feature set, scalability and performance that ESX delivers and no other vendor is offering a small Type 1 hypervisor layer. Not yet at least, until Microsoft releases Longhorn, which should include Windows Server virtualization Update: As Randy Bias correctly points out, there are indeed other Type 1 hypervisors available. Sorry about that!

Desktop Virtualization

As the header suggests, this category is primarily aimed at the desktop user. Most common usage scenarions include development, testing and help desk environments. These products lets you create a virtual instance of a desktop OS, but does not offer the scalability or performance boosts that Server Virtualization products give you. Desktop virtualization products offer other benefits though, like sound card mapping, USB support and other "desktop" features often not provided in the server editions of the virtualization software. The main contenders in the Desktop Virtualization field are:

• VMware Workstation
• Microsoft Virtual PC

Choosing between the two products that seemingly offer similar capabilities basically boils down to a few basic points; Do you need 64Bit Linux support or Cloning/Snapshot functionality? If so, go with VMware Workstation. If not, the choice is basically whatever you feel more comfortable using. In VMware's case their Workstation product is where new and cool features often appear first. VMware Workstation was the first virtualization product that offered snapshot capabilities for quickly restoring a VM to known good state, the same goes for USB support and sound card mapping.

Application Virtualization

Application virtualization is not as hyped as server virtualization, but thats probably about to change as several vendors are lining up in this area as well. Microsoft's acquisition of Softgrid means that application virtualization will be main stream technology very soon. So far the contenders in this field are:

• Microsoft Softgrid
• Altiris Software Virtualization Solution

Both of these offer a very tempting scenario; Zero footprint software installation and management. In a Software Virtualization environment it's not the hardware thats being virtualized, but the part of the OS that the application touches. The virtualized layer is registry settings and configuration settings. Both Softgrid and Altiris Software Virtualization Solution provides a way to run applications inside their own “bubbles”, where they remain “boxed in” and unable to touch the underlying OS or other applications not running inside the same sphere. This way you can run bundle applications that work together in their own packages and distribute those. If you need to upgrade the package, you do it centrally and then distribute it to your clients. Citrix' project Tarpoon is also aimed at the same market, but I can't comment on that as I haven't been able to test it yet and it's still in beta.

Virtual Appliances

Last but not least, Virtual Applianceshas made a big splash in 2006, and will probably continue to do so in 2007 as well. VMware's initiative to make pre-configured appliances available for download has so far resulted in over 300 pre-configured appliances available. Even Microsoft has seen the value of this, and they are currently offering a few test appliances on their own. For more information about the historical aspects of virtualization, and more details the technicalities between the different virtualization options available be sure to have a look at Virtual Linux posted by Tim Jones.

Posted by Christian Mohn aka h0bbel