Three Types of Server Virtualization Explained
Server virtualization has its fair share of benefits for a business – maximizing the IT capabilities, saving physical spaces, and cutting costs on energy and new equipment. But for a company that’s just starting to explore the realm of server virtualization, choosing one from the three types of server virtualization can be daunting.
So what are the three types of server virtualization and how do companies utilize them? Most companies use either full virtualization, para-virtualization, and OS-level virtualization. The difference lies in the OS modification and hypervisor each type employs.
Understanding Server Virtualization: What it is and How it Works
Server computers are powerful – they manage computer networks, store files, and host applications. But most of the time, these powerful processing units are not utilized to their full potential because businesses tend to purchase more computers and other hardware instead, which is not always the wise decision because it occupies more physical space and consumes more energy.
Server virtualization offers one solution to these two problems by creating multiple virtual servers in one physical server. This method ensures that each processing unit is maximized to its full capacity, preventing the need for more computer units in a data center. The adoption of different virtualization technologies, including server virtualization is expected to rise up to 56% by 2021.
Currently, there are three types of virtualization used for sharing resources, memory, and processing.
Full Virtualization
This type of virtualization is widely utilized in the IT community because it only involves simple virtualization. It makes use of hypervisors to emulate an artificial hardware device along with everything it needs to host operating systems.
In full virtualization, separate hardware emulations are created to cater to individual guest operating systems. This makes each guest server fully functional and isolated from the other servers in a single physical hardware unit.
What’s great about this type is that you can run different operating systems in one server, since they are independent of each other. Modification of each OS also isn’t necessary for the full virtualization to be effective.
Currently, enterprises make use of two types of full virtualization:
- Software Assisted Full Virtualization
Software-assisted full virtualization uses binary translation when trapping and virtualizing the execution of instruction sets. The binary translation also emulates the hardware by utilizing software instruction sets. Here’s a list of software under this type:
- VMware workstation (32-bit guests)
- Virtual PC
- VirtualBox (32-bit guests)
- VMWare Server
- Hardware-Assisted Full Virtualization
On the other hand, hardware-assisted virtualization eliminates the need for binary translation. Instead, the original hardware is directly interrupted by the virtualization technology found on the X86 Processors (Intel VT-x and AMD-V). Depending on the guest OS’s instructions, privileged instructions can be executed directly on the processor.
This type of full virtualization can use either of the two hypervisor types:
- Type 1 Hypervisor – also known as the bare-metal hypervisor type, lays directly on top of the physical server and its hardware. Since there is no software of the operating system between the two, Type 1 can provide excellent stability and performance.
Since Type 1 hypervisors are relatively simple, there isn’t much functionality to them. Moreover, once this hypervisor is installed on the hardware, the latter cannot be utilized for anything else except virtualization. Type 1 hypervisors include:
- VMware vSphere with ESX/ESXi
- Kernel-based Virtual Machine (KVM)
- Microsoft Hyper-V
- Oracle VM
- Citrix Hypervisor
- Type 2 Hypervisor – also known as the hosted hypervisor type, is installed inside the operating system of the host machine. Unlike the Type 1 hypervisor, this one has one software layer underneath.
The Type 2 hypervisor is typically used in data centers that only have a small number of physical servers. What makes it convenient to use is that it isn’t much different from the applications in the current operating system. It’s easy to set up and manage multiple virtual machines once the hypervisor has been installed. Here are some of the type 2 hypervisors in the market:
- Oracle VM Virtualbox
- VMWare Workstation Pro/VMWare Fusion
- Windows Virtual PC
- Parallels Desktop
Para-Virtualization
Para-virtualization is a type similar to full virtualization because it also uses the host-guest paradigm. The only main difference is that the guest systems are aware of each other’s presence and they all work as one entire unit.
This type is also time efficient and less intrusive since the virtual machines do not trap on privileged instructions. The operating systems acknowledge the hypervisor used in the hardware, sending the comments – known as hypercalls – in a more direct way.
To exchange the hypercalls between hypervisors and operating systems, both of them must be modified through implementing an application programming interface (API).
Sine paravirtualization utilizes a slightly different hypervisor than full virtualization, here are some of the more common products that support it:
- Xen
- IBM LPAR
- Oracle VM for SPARC (LDOM)
- Oracle VM for X86 (OVM)
OS-level Virtualization
Unlike the first two types of server virtualization, OS-level virtualization doesn’t use a hypervisor and doesn’t apply a host-guest paradigm. Instead, it utilizes a process called “containerization” which creates multiple user-space instances (containers or virtual environments) through a kernel in the OS.
A specific container can only utilize the amount of resources allocated for them, not the available resources for the primary OS. Programs can also run in the container but the access to content is only limited to everything associated with that container and the devices assigned to it.
In this virtualization, kernels and operating systems can have different versions of OS from the host – for example, if the host server runs on Linux, the kernels and OS can only use different versions of Linux and not Windows. Otherwise, the OS-level won’t work.
Here are some of the commonly used containers in the market:
- Oracle Solaris
- Linux LCX
- AIX WPAR
What to Consider for Server Virtualization
Server virtualization is a promising method that can maximize the use of IT resources – that’s why tech giants like Microsoft, Dell, and IBM are continuously developing this technology. However, before picking the optimal virtualization for a business, it’s important to determine their benefits and disadvantages first.
| Pros | Cons | |
| Full Virtualization | It can support different and unmodified operating systems on one physical server. | To prevent the slowing down of applications, you will need to allocate a big part of the physical server’s processor for the hypervisor. |
| Para-virtualization | Para-Virtualized servers don’t need as much space for processing in the physical server. | The operating system of guest servers needs modification to be able to communicate hypercalls with the host. |
| OS-Level Virtualization | It does not need a hypervisor, therefore no additional space requirement needed for processing. | To build a homogenous environment, you are required to install the same operating system on all guest servers. |
Aside from the virtualization method, you should also consider the following factors before settling on a specific type:
- OS Rebooting – Operating system rebooting is typically overlooked because OS are expected to work all the time. However, there is still a small risk of OS crashes. If this happens, an independent OS reboot must be possible.
- Deployment Work – While the type 2 hypervisor is easy to implement, it’s not the same case for type 1 hypervisor. The bare-metal hypervisor is much more difficult to handle than the former, so a thorough integration process is needed – especially for large deployments.
- Multiprocessing – Before selecting the virtualization solution, check first it includes symmetric multiprocessing support (SMP) for multiple processors of the same type or asymmetric multiprocessing support (AMP) for multiple processors of a different type. Some virtualization infrastructures also come with both SMP and AMP combined.
Adopt Server Virtualization for Your Company with Abacus
Thousands of companies are turning to server virtualization as a cost-effective IT strategy, so why not do the same?
With our team of IT experts at Abacus, we will help you maintain optimal efficiency in your office. Enhancing business productivity starts with the right technological solution. Take the first step with us in reaching the top. Contact (856) 505 6860 or email info@goabacus.com now for your first consultation.
