This post is the second in a series on virtualization: Introduction, Platform (Servers and PCs), Desktop, Application, and Cloud

Of my four rough categories of virtualization, platform or server virtualization is usually what comes to mind first. I use the term platform since this can be done in special situations with PC operating systems, not just server, but I’ll cover those in my next post.
 
Typically, instead of running a server operating system like Linux or Windows Server on its own hardware, you instead run it inside an already running server. Usually this is done on a special server set up to run many virtual servers on a single box. This can also be done on a PC or laptop, but usually with only one guest operating system running inside the main operating system.
 

So why would you do this?

1. Consolidation/Cost: Typical IT datacenters have many, many servers but many of those servers don’t work very hard. There’s lots of spare processing cycles to go around. Consolidation of these servers into less physical boxes saves hardware cost, power, and space. In large datacenters this can add up to huge cost savings for a company, if the profile of the servers being consolidated is right.
2. Flexibility/Dynamic Capacity: Sometimes servers don’t need to be around all that often. A company may need to add capacity only occasionally (like during tax season) or may keep special application servers around only for particular projects. Virtual servers can be moved around much more easily than physical servers and can be stored as images in large data storage. Some companies keep a virtual library of special use server images that can be set up when needed.
3. Development/Testing/Support: Sometimes a PC user may have a need for a special use operating system on their own PC. I’ve done this often for demo purposes, even running a virtual server OS on my laptop at times to show of some scenario or capability. This is also often used to host special development or testing environments. Finally, some critical or interesting pieces of software may not run on your main operating system and so a virtual guest environment may be useful (e.g. Windows on a Mac or Linux on a Windows PC.)

Server Virtualization – Industry Roundup

Here’s a rundown of some of the main players in platform virtualization and a high-level analysis of each:

Citrix – XenServer 

• Was focused on the open-source Xen project but now provides Hyper-V managementBase, relatively full featured version available free as Xen
• Enterprise support and advanced management provided at enterprise cost
• Seen as enterprise class and a viable competitor to VMWare and MS Hyper-V (as well as a MS partner against VMWare) especially at lower price points, but requires Citrix management tools to be used effectively

EMC – VMWare

• Market leader with majority market share and high penetration in large businesses
• Known for unique (for now) advanced enterprise features like memory overcommit Free starter-style version available as ESXi
• Seen as the market leader though costs can be high and alternatives may have strengths in specific circumstances

IBM – z/VM

• Traditionally a mainframe based OS virtualization technology
• Based on deep history of OS virtualization development dating back to the 1960s
• Focused on UNIX/Linux OS support
• Seen as a strong UNIX/Linux solution for datacenters already managing large IBM platforms or datacenters outsourced to IBM but not typically considered for new implementations

Microsoft – Hyper-V

• Second place in market share and gaining on VMWare
• Near feature parity with all other vendors, requires MS management tools for full capabilities
• Free console managed version and full version available with Windows Server
• Seen as a strong contender for leadership in virtualization in the future and often wins on price but still lacks some of the enterprise capabilities of competitor offerings

Open Source – Xen 

• Capable, open-source virtualization offering
• Feature parity at the hypervisor level with other enterprise offerings
• Lacks management tools and support needed in most enterprise environments
• Seen as a strong hypervisor platform but mostly adopted through enterprise vendors building solutions around it, like Citrix and Oracle

Oracle – VM Server

• Xen based offering targeted at Oracle solutions
• May be a stronger offering in the future with the integration of Sun multi-OS solutions
• Seen as a follower in this space but a viable alternative for heavy Oracle shops

With that roundup I’ll break for now and cover PC level platform virtualization in my next post. Until then let me know if you have any comments or see any gaps. Enjoy!