Responsi Paul's List: Virtualization

• Selecting a virtualization hypervisor begins with an important choice: Do you need a hosted or bare-metal hypervisor? Once you decide which type of hypervisor you need, there are lots of factors to consider.
• Here are eight considerations for choosing a virtualization hypervisor:
• Performance
   If you want high performance, a bare-metal virtualization hypervisor is really your only option.
• Hosted hypervisors typically have no or limited resource controls, so VMs have to fight each other for resources.
• Hardware compatibility
   Hosted hypervisors tend to facilitate hardware compatibility because they run on Windows or Linux, and you can almost always find a device driver for a host running those OSes. Some bare-metal virtualization hypervisors, such as VMware ESX and ESXi, work with a limited set of certified hardware. Microsoft Hyper-V does not have this restriction, however, because any driver that works with Windows will work with Hyper-V.
• Ease of use
   Hosted virtualization hypervisors are also easy to install, use and maintain. Plus, they typically do not require specialized skills. Most hosted hypervisors install like an application and are fairly intuitive.
• With a bare-metal hypervisor, you really need to know what you’re doing.
• High availability
   Bare-metal virtualization hypervisors offer high-availability features, which provide continuous availability in the event of a host failure. VMware has numerous availability features, including vMotion, VMware High Availability and Fault Tolerance.
• Hosted virtualization hypervisors typically lack high-availability features, so if a host fails, VMs are down until you resolve the problem.
• Reliability
   When it comes to reliability, bare-metal hypervisors definitely have an edge.
• Virtualization hypervisor management
   Bare-metal virtualization hypervisors have more options for management and automation. They have centralized consoles that allow you to easily manage large numbers of hosts and VMs.
• Hosted hypervisors, on the other hand, tend to be islands that admins have to manage individually
• Cost
   When it comes to cost, hosted virtualization hypervisors have a big edge over bare-metal hypervisors.

• Scalability
   If you want scalability, a bare-metal virtualization hypervisor is the only way to go. A bare-metal hypervisor can scale very high, something VMware especially focused on in vSphere 5. In vSphere 5, you can create single VMs with up to 1 TB of memory and 32 virtual CPUs, which should satisfy any workload. With bare-metal hypervisors, you can easily run hundreds of VMs on a single host if you have enough hardware resources.

    

  In contrast, hosted hypervisors have very limited scalability, both in the size of the VMs and the number of VMs that can run on a single host. VMware’s hosted virtualization hypervisor, Workstation, can only support VMs with up to 32 GB of memory and 8 virtual CPUs.

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