Virtualisation is a framework or methodology of dividing the resources of a computer into multiple execution environments, by applying one or more concepts or technologies such as hardware and software partitioning, time-sharing, partial or complete machine simulation, emulation, quality of service, and many others.
Typically, in order to virtualize, you would use a layer of software that provides the illusion of a "real" machine to multiple instances of "virtual machines". This layer is traditionally called the Virtual Machine Monitor (VMM) or “hypervisor”.
The hypervisor could run directly on the real hardware or it could run as an application on top of a host operating system.
Type 1 VMM IBM CP/CMS VMware ESX Windows Virtualisation (2008) Xen Virtual Iron Hardware VMM Guest VM Guest VM Guest VM
Type 2 VMM VMware Server Hardware VMM Guest VM Guest VM Guest VM Host OS
Hybrid VMM MS Virtual Server MS Virtual PC Hardware VMM Host VM Guest VM Guest VM
Centralized Management: Reports Full set of reports, integration with MOM database Actions one click away in context sensitive Actions Pane
Self Service Portal Ability to control owned virtual machines Thumbnails of all owned virtual machines
Self-Service Portal Provisioning User selects from list of templates Administrator has associated with that user
Self-Service Portal Provisioning New virtual machine ready for use, Terminal Services connection information automatically emailed to user.
Virtual Server 2005 vs Windows Server Virtualization Virtual Server 2005 R2 Windows Server Virtualization 32-bit VMs? Yes Yes 64-bit VMs? No Yes Multi-processor VMs? No Yes, up to 8 processor VMs VM memory support? 3.6 GB per VM More than 32 GB per VM Hot add memory/processors? No Yes Hot add storage/networking? No Yes Can be managed by System Center Virtual Machine Manager? Yes Yes Microsoft Cluster support? Yes Yes Scriptable / Extensible? Yes, COM Yes, WMI Number of running VMs? 64 More than 64. As many as hardware will allow. User interface Web Interface MMC 3.0 Interface
XenSource Products N/A N/A Mid-2007 Shared storage N/A N/A Mid-2007 Live Migration Red Hat EL 3.6, 3.7, 3.8, 4.1, 4.2, 4.3, 4.4, 5.0; SUSE SLES 9.2, 9.3, 10.1; Debian Sarge N/A (Windows guests support only) Red Hat EL 3.6, 3.7, 3.8, 4.1, 4.2, 4.3, 4.4, 5.0; SUSE SLES 9.2, 9.3, 10.1; Debian Sarge Linux guest support Windows Server 2003; Windows XP; Windows 2000 Server Windows Server 2003; Windows XP; Windows 2000 Server Windows Server 2003; Windows XP; Windows 2000 Server Windows guest support Developers, testers, support, IT enthusiasts Windows IT professionals Enterprise IT, system integrators User Profile
An enterprise ready native virtualisation platform
Uses hardware-assisted virtualisation technologies of Intel VT and AMD-V processors
Based on an open source hypervisor derived from the Xen open source project
No software need be installed on physical hardware
Virtual Iron Components Operating systems that are fully virtualised on a physical server Varies Guest operating systems Controls virtual servers through an agent in the service partition Commercial Virtualisation Manager Second software loaded when physical server boots. Manages virtual server creation and configuration and all I/O. GPL Service Partition First software loaded when physical server boots. Manages all hardware resources GPL Hypervisor Function License Component
LiveMigration – moves a running virtual server from one physical server without pausing or impacting running applications
LiveCapacity – monitors virtual server CPU utilisation or other application needs to determine when a workload needs additional capacity. When a user-defined threshold is met, the virtual server is LiveMigrated to a physical server that has the necessary resources
LiveRecovery – monitors the status of physical resources and moves virtual servers to maintain uptime in the event of a hardware failure
LiveMaintenance – moves virtual servers to alternative locations without downtime when a physical server is taken offline for maintenance
Supported Configurations Up to 16 Virtual disks per virtual server Up to 5 Virtual NIC adapters per virtual server Up to 5 Virtual servers per physical server CPU Up to 96GB RAM per Physical Server Up to 8 Processors per virtual Server 100s per virtual data centre Virtualised Nodes Intel Xeon with Intel VT AMD Opteron with AMD-V Processors 32 and 64-bit Red Hat Enterprise Linux 4 32 and 64-bit SUSE Linux Enterprise Server 9 32-bit Windows XP 32-bit Windows 2003 Operating systems Support Feature