The selection of the right hypervisor starts with an important decision; do you believe that a bare-metal hypervisor or a hosted hypervisor is the right choice for you? This is the first important decision that you need to confront and you need to be prepared to deal with a number of other important issues that you will need investigate and decide upon in order to make sure that you make the right choice of the hypervisor that will exactly respond to your needs.

Make a check list of the important research that you will need to do, satisfy yourself that you have:

• Understood the difference between hosted and bare-metal virtualization hypervisor types
• Investigate and research which one is right for you
• Does your hoster offer the virtualization hypervisor as a commodity?
• How secure is your hypervisor, are you going to be vulnerable and at risk. What is the scale of this security risk?

Initial objectives

Make a clear checklist that includes:

• Makes sure your virtualization hypervisor is 100% compatible with the hardware platform that you have available.
• Insist on excellent performance, simple management and an ability to be integrated into your virtual infrastructure.
• What about high availability? You will need to consider which are the best industry leading and price performing load balancers or application delivery controllers (ADCs) available in the market today, these are vitally important to deliver your project and keep your servers up and running.
• Reliability
• Scalability
• Last but by no means not least cost, not only of deployment but also the cost of keeping these hypervisors running should never be underestimated.

Choices for performance

If it is high performance that you need and advanced resource control you should take into account that your best option for virtualization is going to be a bare metal hypervisor. The reason for this is that the bare metal hypervisors use the smallest amount of resource overhead while at the same time giving you the advantage of being able to prioritize or restrict virtual machine (VM) usage and guarantee VM resource allocation.

On the other hand hosted hypervisors normally have limited or even no resource control. This means that VMs need to compete with each other to grab resources. Another limiting factor is that hosted hypervisors unlike their bare metal cousins frequently have heavy resource overhead penalties. This is particularly the case when tools, operating system services and applications are also running on the guest system.

Comparing the costs

In order to calculate the correct costs for the hypervisor you are considering using the first thing that you should keep in mind at all times is that hosted hypervisors will come in at considerably reduced prices compared with bare metal hypervisor. Typically you should be looking at spending only a few hundred dollars or even should get free hypervisors from your provider. Bare metal hypervisors are going to cost you a great deal more particularly if you want to choose a system that can scale up so that you can implement advanced features. Dig under the surface of the prices that you are being offered for bare metal hypervisors, they may initially seem low cost or even free, but should you want to use management utilities and advanced features you could be facing a bill for thousands of dollars.

Advantages of hosted hypervisors

Running on Windows or Linux hosted hypervisors offer greater hardware compatibility than bare metal virtualization hypervisors, this is because servers are designed with support of these operating systems in mind. Bare metal virtualization hypervisor device drivers for ESXi, EXE and VM-Ware do exist but you will find that the choice of hardware platforms is more limited. Microsoft Hyper V offers an advantage because it will work with any windows driver that may be compatible with your hardware platform.

Question of ease of use

One of the great advantages of hosted virtualization hypervisors is that they are easy to install, straightforward to use and do not require specialist skills to maintain. The fact that a specialist is not needed in your IT team to maintain these servers has obvious economic benefits. Installation of the majority of hosted hypervisors is similar to that of a windows application and therefore can be considered intuitive. On the other hand bare-metal virtualization hypervisors are normally quite straight forward to install but things start getting tricky when it is time to configure the hypervisor. Thanks to the amount of freedom that you have during the configuration it is all too often easy to make a mistake and your hypervisor will not work at all or will not work correctly. It is essential that you really do know what you’re doing when it comes to installing bare metal virtualization hypervisors. 

The most reliable hypervisors

Considering the question of reliability as a rule bare metal hypervisors will generally offer you a better solution compared with hosted virtualization hypervisors. The main reason for this is that the bare metal virtualization hypervisor is normally subject to far more stringent tests and QA procedures that their hosted counterparts. This is not just to satisfy the manufacturers that their hypervisors are superior but to deal with an operational requirement. The fact is that bare metal hypervisors are targeted at data centers that cannot allow for any bugs or other performance issues. A second important consideration is that with no host operating system residing on the bare metal hypervisor there is one less element to worry about failing in the hypervisor.

A cause of hypervisor failures can be the hardware drivers and this failure can affect both hosted as well as bare metal hypervisors. Once again there is a difference between the hosted and bare metal hypervisor testing. Hosted drivers are normally subject to a standard testing cycle before deployment whereas a number of bare metal hardware drivers for example ESXi, ESX and VMware require rigorous testing before the hardware driver is considered to merit a hardware certificate.

Plan for high availability

You effectively have two choices of where to place your high availability, either in the virtualization hypervisors themselves or to deploy load balancers, both virtual or hardware appliances that offer this functionality. High availability ensures business continuation even in the event that a virtualized hypervisor fails. vMotion from VMware is considered to one of the best high availability solutions as it comes packed with features fault tolerance is also included. Microsoft Hyper-V has improved its high availability options recently but is considered by some to be a less integrated solution compared with VMware. XenServer from Citrix needs to rely on other third party products to be set up in high availability mode. Hosted virtualization hypervisors don’t normally come with high availability options, for this reason you should consider using dedicated virtual or physical load balancers to deal with any VM failures that may occur.

Management options for virtualization hypervisors

Essentially you will find a better set of management and automation tools for bare metal virtualization hypervisors. Consoles can be centralized to provide a single dashboard that makes it easier to monitor a larger number of VMs and hosts. A second advantage for the bare metal option is the large number of 3^rd party automation and management tools that are available too. Hosted hypervisors need to be individually managed and this limitation makes management that much more time consuming and laborious when you have large infrastructures.

A question of scale

When considering scalability bare metal hypervisors win every time over hosted hypervisors. A bare metal hypervisor is designed to scale to extreme upper limits. Study VMware’s vSphere 5 if you want to understand the potential power that can be available to you. Individual VMs with as much as 1TB of memory powered by up to 32 virtual CPUs address even the largest performance requirements. You will understand that you can activate one, two or more hundreds of VMs on a single physical server by simply having purchased enough hardware capacity. Hosted hypervisors don’t offer such power options. Check out VMware’s capacities that can be run on a single hosted hypervisor and you will immediately understand the greater limitations.