Virtualisation was once found almost exclusively in large data centres. These days it can be found in many small to medium size businesses, thanks in part to powerful lower end servers and the advent of “free” virtualisation software.
Server Virtualisation comes in two main forms:
- Host based virtual machines that run on top of an existing operating system e.g. VMware workstation, Microsoft Virtual PC, Sun VirtualBox and Parallels Desktop.
- Hypervisor systems where the Virtualisation layer sits directly on top of the physical hardware and doesn’t require a host operating system. e.g. Microsoft Hyper-V Server, VMware ESX and Citrix XenServer.
Hyper-V Server 2008 is available as a free download and is essentially a modified version of Windows 2008 Server Core without the ability to add roles other than Hyper-V. The user interface is PowerShell command line only i.e. no GUI. A remote management console can be used to configure the Hyper-V environment or for larger environments you have the choice of either System Centre Virtual Machine Manager (SCVMM) or Citrix Essentials for Hyper-V.
- x64 Based Intel (with VT extensions) or AMD (with AMD-V extensions) CPU
- Data Execution Prevention must be enabled in hardware
- 2GB RAM plus RAM for each guest Operating System
- Either Hyper-V Server or a copy of Windows 2008 Standard, Enterprise or Datacentre
Note that you shouldn’t automatically assume all server hardware will support Hyper-V. In some cases it may be necessary to update firmware or install hardware vendor supplied updates.
Hyper-V systems can host a number of different operating systems include:
- Windows 2003 and 2008 Server 32bit and 64bit Editions
- Windows Vista SP1
- Windows XP SP2 or later
- SuSE Enterprise Linux (other versions of Linux may work but are not supported)
Hyper-V is currently in its first release and as such has a number of limitations when compared to VMWare ESX. Limited support for hardware pass through e.g. SCSI tape devices can’t be accessed from Hyper-V hosts but some USB devices can. Hyper-V doesn’t currently have a VMotion type function used in high-availability systems. Many of these features are enterprise type functions and may not be needed in small to medium size networks and given the cost of getting those features these limitations are accepted by many people.
Some applications may not be supported in a virtual environment and this should be taken into consideration when designing a solution. Applications that require high disk I/O are often in this category, this doesn’t mean they won’t work but you may not get the level of performance you would expect.
Watch this space:
Windows 2008R2 is due for release on the 22nd of October 2009 and will feature many improvements to Hyper-V. One of the key new features is Live Migration which provides VMotion type functionality and will help narrow the feature gap. Hyper-V is a hot technology and a key part of Microsoft’s network strategy and as such I am sure we will continue to see rapid improvement in functionality in the future.