Virtual vs Physical Performance

Virtualization helps increase the utilisation and efficiency of IT hardware. However, there are many important differences between virtual machines and physical computers when it comes to performance.

Virtualized Server vs. Traditional Server

• Most servers in production today run only a single application. While this approach ensures the smooth operation of the application, it uses only a fraction of the IT resources available on the underlying hardware.

• Virtualization makes it possible to run several applications at the same time on a single physical server by hosting each of them inside their own virtual machine. By running multiple virtual machines simultaneously, a physical server can be driven to much higher utilisations, albeit with some performance overhead.

Availability

• Virtual machines that reside on the same physical server share underlying hardware resources, but are completely isolated from each other as if they were physically separated. This means that if one virtual machine experiences availability problems, it will not affect the availability of applications running on the other virtual machines on the server.

• In the event that the underlying hardware itself experiences performance or availability problems, VMware provides the ability to migrate live applications automatically from one physical server to another with no interruption in service.

• This capability holds enormous advantages over physical infrastructures when it comes to backup and recovery, but VMware also leverages live migration to enable exclusive capabilities such as dynamic policy-based allocation of hardware resources.
  

Resource Allocation

VMware solutions virtualize four key hardware resources: processing, memory, storage and network, using a best-of-breed hypervisor to allocate these resources dynamically to balance changing application needs.

	The VMware 'Hypervisor'

• Performance Implications for CPUs - VMware solutions have the ability to balance processor loads in a highly efficient manner, and VMware virtual machines can fully leverage multi- cores and multi-processor configurations, making it possible to run processor-intensive workloads such as databases and e-mail servers on virtual machines without adversely affecting application performance.
  
  
• Performance Implications for Memory (RAM) - VMware technology offers advanced memory management mechanisms such as RAM over-commitment and transparent page sharing that automatically expand or contract the amount of RAM allocated each virtual machine as application loads increase and decrease. This capability lets you achieve a higher level of server consolidation than is possible with traditional static virtual memory.
  
  
• Performance Implications for Storage - VMware solutions help to improve I/O performance through the VMware Virtual Machine File System (VMFS), which provides virtual machines with simultaneous access to shared data stores. Centralised storage helps reduce latency and increase throughput, and provides the foundation for unique capabilities such as live migration and consolidated backup.
  
  
• Performance Implications for Networking - VMware offers an ideal platform for secure, high-speed networking between virtual machines on a single physical server, supporting network topologies that normally depend on the use of additional hardware to provide security and isolation. You can also network virtual machines across physical servers with transparency and high throughput, as each virtual machine gets its own IP address and can utilise up to four virtual network interface cards (NICs).

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