Recently, users are increasingly hearing about such a concept as “virtualization”. It is believed that its use is cool and modern. But far from every user clearly understands what virtualization is in general and in particular. Let's try to shed light on this issue and touch on server virtualization systems. Today it is these technologies that are cutting-edge because they have many advantages in terms of both security and administration.
What is virtualization?
Let's start with the simplest - defining a term that describes virtualization as such. We note right away that on the Internet you can find and download some kind of manual on this issue, such as the “Server Virtualization for Dummies” manual in PDF format. But when studying the material, an unprepared user may encounter a lot of obscure definitions. Therefore, we will try to clarify the essence of the issue, so to speak, on the fingers.
First of all, when considering server virtualization technology, we dwell on the initial concept. What is virtualization? Following simple logic, it is easy to guess that this term describes the creation of a certain emulator (similarity) of some physical or software component. In other words, this is an interactive (virtual) model that does not exist in reality. However, there are some nuances.
The main types of virtualization and technologies used
The fact is that in the concept of virtualization there are three main areas:
- representation;
- Applications
- servers.
For understanding, the simplest example may be the use of so-called terminal servers, which provide users with their own computing resources. The user program runs on the remote server, and the user sees only the result. This approach reduces the system requirements for the user terminal, the configuration of which is outdated and cannot cope with the given calculations.
For applications, such technologies are also widely used. For example, it could be virtualization of a 1C server. The essence of the process is that the program runs on a single isolated server, and a large number of remote users gain access to it. The software package is updated from a single source, not to mention the highest level of security for the entire system.
Finally, it implies the creation of an interactive computer environment, server virtualization in which fully repeats the real configuration of the "iron" brothers. What does this mean? The fact is that, by and large, on one computer you can create one or more additional ones that will work in real time, as if they existed in reality (server virtualization systems will be discussed in more detail a little later).
Moreover, it does not matter at all which particular operating system will be installed on each such terminal. By and large, this has no effect on the main (host) OS and virtual machine. This is similar to the interaction of computers with different operating systems on the local network, but in this case, virtual terminals may not be interconnected.
Equipment selection
One of the obvious and undeniable advantages of virtual servers is the reduction of material costs for creating a fully functional software and hardware structure. For example, there are two programs that require 128 MB of RAM for normal operation, but they cannot be installed on one physical server. What to do in this case? You can purchase two separate 128 MB servers and install them separately, or you can buy one with 128 MB of RAM, create two virtual servers on it and install two applications on them.
If someone still does not understand, in the second case, the use of RAM will be more rational, and material costs are significantly lower than when buying two independent devices. But this is not the only thing.
Security Benefits
As a rule, the server structure itself implies the presence of several devices to perform certain tasks. In terms of security, system administrators install Active Directory domain controllers and Internet gateways not on one, but on different servers.
In the event of an external intervention attempt, the gateway is always the first attack. If a domain controller is also installed on the server, then the probability of damage to AD databases is very high. In a situation with targeted actions, all of this can be taken over by attackers. Yes, and restoring data from a backup is a troublesome business, although it takes relatively little time.
If you approach this issue on the other hand, it can be noted that server virtualization allows you to bypass installation restrictions, as well as quickly restore the desired configuration, because the backup is stored in the virtual machine itself. True, it is believed that server virtualization with Windows Server (Hyper-V) in this view seems unreliable.
In addition, the licensing issue remains quite controversial. For example, for Windows Server 2008 Standard, only one virtual machine can be launched, four on Enterprise, and an unlimited number on Datacenter (and even copies).
Administration Issues
The advantages of this approach, not to mention the security system and cost reduction, even when virtualizing servers with Windows Server, should first be appreciated by system administrators who service these machines or local networks.
Very often, creating backups of the system becomes a stumbling block . Usually, when creating a backup, third-party software is required, and reading from optical media or even from the Web takes longer than the speed of the disk subsystem. Cloning the server itself and the virtual machine can be done in just a couple of clicks, and then quickly deploy a functioning system even on "clean" hardware, after which it will work without failures.
In VMware vSphere, server virtualization allows you to create and save so-called snapshots of the virtual machine itself, which are special images of its state at a particular point in time. They can be represented in a tree structure in the machine itself. Thus, restoring a virtual machine is much easier. In this case, you can arbitrarily select recovery points, rolling the state back and then forward (Windows-systems can only dream of this).
Server Virtualization Programs
If we talk about software, here you can use a huge number of applications to create virtual machines. In the simplest case, native tools of Windows systems are used, with the help of which server virtualization can be performed (Hyper-V - built-in component).
However, this technology also has some drawbacks, so many people prefer software packages like WMware, VirtualBox, QUEMI, or even MS Virtual PC. Although the names of such applications differ, the principles of working with them are not particularly different (except in the details and some nuances). With some versions of applications, Linux server virtualization can also be performed, but these systems will not be considered in detail, since most of us use Windows after all.
Server Virtualization on Windows: The Simplest Solution
Since the release of the seventh version of Windows, a built-in component called Hyper-V has appeared in it, which made it possible to create virtual machines using the system’s own resources without using third-party software.
As in any other application of this level, in this package you can simulate a future virtual computer by specifying the size of the hard disk, the amount of RAM, the presence of optical drives, the desired characteristics of a graphic or sound chip - in general, all that is in the hardware regular server terminal.
But here you need to pay attention to the inclusion of the module itself. Hyper-V server virtualization cannot be performed without first enabling this feature on the Windows system itself.
In some cases, it may be necessary to activate the support of the corresponding technology in the BIOS.
Using third-party software products
Nevertheless, even despite the means by which virtualization of Windows-system servers can be performed, many experts consider this technology to be somewhat inefficient and even excessively complicated. It is much easier to use a ready-made product in which similar actions are performed on the basis of automatic selection of parameters, and the virtual machine has great capabilities and flexibility in management, configuration and use.
We are talking about the use of such software products as Oracle VirtualBox, VMware Workstation (VMware vSphere) and others. For example, a VMware virtualization server can be created in such a way that analogs of computers made inside a virtual machine work separately (independently of each other). Such systems can be used in training processes, testing of any software, etc.
By the way, it can be noted separately that when testing software in a virtual machine environment, you can even use virus-infected programs that will only show their effect on the guest system. On the main (host) OS, this will not affect in any way.
As for the process of creating a computer inside the machine, in VMware vSphere, server virtualization, as well as in Hyper-V, is based on the “Wizard”, however, if you compare this technology with Windows-based systems, the process itself looks a little easier, since the program itself may offer some kind of templates or automatically calculate the necessary parameters of the future computer.
The main disadvantages of virtual servers
But, despite how many advantages the server system gives to the same system administrator or end user, such programs have some significant disadvantages.
Firstly, you won’t jump above your head. That is, the virtual machine will use the resources of the physical server (computer), and not in full, but in a strictly limited amount. Thus, for the virtual machine to work properly, the initial configuration of the hardware must be powerful enough. On the other hand, the purchase of one powerful server will still come out much cheaper than the purchase of several with a lower configuration.
Secondly, although it is believed that several servers can be combined into a cluster, and if one of them fails, you can "move" to another, but in Hyper-V it is impossible to achieve this. And it looks like a clear minus in the issue of fault tolerance.
Thirdly, the issue of transferring resource-intensive DBMS or systems like Mailbox Server, Exchange Server, etc. to the virtual space will be clearly controversial. In this case, there will be a clear inhibition.
Fourth, for the correct operation of such an infrastructure, you cannot use exclusively virtual components. In particular, this applies to domain controllers - at least one of them must be “hardware” and initially available on the Web.
Finally, fifthly, server virtualization is fraught with another danger: the failure of the physical host and host operating system will entail the automatic shutdown of all related components. This is the so-called single point of failure.
Summary
Nevertheless, despite some disadvantages, the advantages of such technologies are clearly greater. If you look at the question of why server virtualization is needed, here you can highlight several main aspects:
- reduction in the number of "iron" equipment;
- reduced heat and energy consumption;
- reduction of material costs, including the purchase of equipment, payment for electricity, the purchase of licenses;
- simplified maintenance and administration;
- the ability to "migrate" the OS and the servers themselves.
Actually, the benefits of using such technologies are much greater. Although it may seem that there are some serious shortcomings, with the proper organization of the entire infrastructure and the use of the necessary controls for smooth operation in most cases, the appearance of such situations can be avoided.
Finally, for many, the question of choosing software and the practical implementation of virtualization remains open. But here it is better to turn to specialists for help, since in this case we had exclusively the issue of general familiarization with server virtualization and the advisability of introducing the system as such.