Server virtualization refers to the technology of using virtualization software to build multiple virtual servers on a single physical server. This server virtualization mechanism is roughly divided into two types: “host OS type” and “hypervisor type”.This time, I will explain the virtualization mechanism of those servers and their advantages and disadvantages.
1. What is server virtualization? As I mentioned briefly at the beginning, server virtualization is the construction of multiple virtual servers on a physical server using software (virtualization software).
And this virtual server is called a “virtual server”.Since there is only one physical server in virtualization, there is only one hardware resource such as CPU and memory. However, since virtualization technology allocates CPU processing amount and memory capacity to each virtual server, the virtual servers do not compete for CPU and memory and operate like independent servers.
2. Technologies and mechanisms that support virtualization “Host OS type”, “hypervisor type”, and “container type” are the three typical technologies and mechanisms that realize virtual servers. Let’s take a closer look at each.
Host OS type Host OS type is a technology to build a server (virtual server) on the virtualization software installed in the OS (host OS) of the physical server. And the OS of this virtual server is called the guest OS. There is no need to prepare a dedicated OS for virtualization, and it can be executed as easily as an application.
Hypervisor type Hypervisor type is a technology to build a virtual server by directly installing virtualization software (hypervisor) on the hardware of the physical server.
Container type The biggest feature of the container type is that it does not start the guest OS. One virtual space is a container that runs on the host OS and container engine and contains all the necessary items for the application.In addition, these three have different processing performance because the mechanism for accessing the hardware is different.
In the case of the host OS type, the virtual server accesses hardware resources such as CPU and memory via the host OS, which causes extra processing (overhead) for the host OS.On the other hand, in the case of the hypervisor type, the hardware resources are accessed via the hypervisor installed directly on the hardware without using the host OS. Therefore, extra processing is suppressed compared to the host OS type, and the virtual server can operate with higher performance.Finally, the container type, which is in the form of host OS + container engine. Unlike the host OS type and hypervisor type, it does not require a guest OS, so the load is small and the operation is fast.Since the host OS type is an old method as a virtual server technology, it used to be the mainstream of server virtualization, but now the hypervisor type, which boasts higher performance, has become the mainstream of virtualization technology. I am. Recently, the number of container types is increasing, and it is becoming a new trend.
3. Benefits of server virtualization There are four benefits to virtualizing a server:
◇ Cost reduction by server consolidation Servers that do little processing at normal times and servers with low operating rates cause wasteful costs. It’s common for servers installed at each of your company’s locations to be inactive.However, if you virtualize multiple servers and consolidate them into one server, you only need one physical server, which can lead to cost reduction.
◇ Space saving As mentioned above, if you build multiple physical servers as virtual servers, you can reduce the number of physical servers and save space.
◇ You can flexibly increase or decrease the number of servers Virtual servers can be built by simply installing and configuring virtualization software, so installation costs can be reduced compared to building physical servers.Also, when the server is no longer needed, the physical server takes the trouble of disposing of it.
However, with virtual servers, you can reduce the number of servers by simply removing unnecessary virtual servers, just like uninstalling software.
The ability to flexibly respond to changes in the number of servers is a major advantage of virtual servers.
◇ Hardware utilization efficiency For virtual servers, CPU and memory usage can be determined by settings. In other words, by changing the hardware resources allocated to each virtual server, it is possible to efficiently operate the server using the hardware resources.
4. Disadvantages of server virtualization On the other hand, there are three disadvantages:
◇ Deterioration of processing performance Since virtual servers access hardware resources via virtualization software, the total processing performance is lower than that of physical servers alone.
Therefore, there is a possibility that the processing speed will slow down due to virtualization.
◇ Difficult to estimate resources While there is an advantage that multiple servers can be virtualized and combined into one, virtual servers share the hardware resources of physical servers.
As a result, hardware resources may run out unexpectedly, so the physical server specs need to be generous.
◇ Failure countermeasures You can use virtualization technology to consolidate multiple servers into a physical server, but if a physical server fails, all virtual servers will be affected. Therefore, it is better to take more careful measures against obstacles.With virtualization technology, servers can be aggregated, which has many advantages. However, on the other hand, it should be remembered that aggregation has disadvantages such as resources and troubleshooting.
Summary Server virtualization has many advantages such as space saving and effective use of resources because multiple servers can be aggregated. There are some downsides to consolidating servers, but think carefully about how you can benefit from virtualization.