Modern systems of computer hardware division into sections are extremely diverse. Here there are many projects whose software can solve important problems associated with the creation of home servers. Moreover, programs and virtualization modules are used not only by hosting providers, they are also able to provide everyday assistance in the work of a system administrator.
Open VZ is a complete virtualization technology based on the Linux software kernel. This operating system has a number of advantages and disadvantages. At the same time, Open VZ supports two modes of operation:
- Creating a VPS server
- Creating a virtual environment VE
Thanks to this software technology, you can create a large number of standalone copies of the system that will work independently of each other. Moreover, like any virtualization tool, Open VZ consumes a certain amount of hardware resources. Compared to other systems, the performance of Open VZ is much higher, and the requirements to stuffing a home computer or server are lower. For this reason, the Open VZ system should be considered as an optimized virtualization tool that can provide flexibility in operation and performance at low cost of hardware resources to support the software component of virtualization.
Open VZ features, typical strengths and weaknesses
High system performance is a typical plus of a virtualization system. However, adaptability to the Linux software kernel makes it less functional than systems from other manufacturers. For this reason, a large number of software patches have been issued to Open VZ, partly solving issues with increasing functionality. Although they are not able to fully provide all the capabilities of a virtual server or virtual environment in the Linux software shell.
Practical advantages of the system
- Ease of administration due to the use of a single kernel for all virtual server processes and environments.
- Flexible scalability and ease of redistribution of hardware resources between virtual servers and environments. In this case, the redistribution of resources is performed without rebooting.
- Lower cost of VPS servers based on Open VZ.
There is also the opinion of system administrators that the system does not waste server performance when creating a VPS or VE because it is only an add-on to the operating system kernel. Therefore, without an optional resource limitation, servers and virtual environments will work without loss of performance, which will not distinguish them from physical servers.
The major disadvantages of Open VZ
- The presence of one Linux kernel, which is why all the processes on the servers are processed by one operating system.
- The inability to install other operating systems on a VPS or VE due to the adaptability of the technology to the Linux software shell.
- Having one file system for all VPS and VE.
Moreover, due to the following shortcomings of the Open VZ system, the possibility of overselling (sharing a new user of the services with the virtual server of the hosting center client), is also conditioned. This is possible if the amount of resources, used to ensure the performance of its web projects, is not fully utilized according to the tariff plan. This disadvantage is practically of no importance for hosting users, since many simply cannot notice a drop in performance. For hosting companies, this feature allows you to reduce the cost of hosting a VPS.
Xen virtualization technology
Xen is a more streamlined and optimized virtualization technology, devoid of many of the disadvantages of Open VZ, although it has its drawbacks. Despite this, at the moment the system of IanPratt, the head of the development process at the University of Cambridge, is a more mobile and streamlined system that allows you to create virtual servers in home computers and server companies.
Initially, the project Xen wore experimental status, and therefore no hope was placed on it. However, the system later became a full-fledged software product, and the development manager himself, IanPratt, became the founder of XenSource. As the project progressed, in 2007 the company passed under the wing of Citrix, and on April 15, 2013 it was taken over by the Foundation.
It is noteworthy that since 2003, two versions of the software have been released: this is the free version of Xen under the GPL license and the commercial XenEnterprise and XenServer. With this, in 2009, it was decided to make commercial products available under an open source license. Since then, the virtualization technology, as well as the application software for its implementation on servers, has become completely free for commercial and home use.
Software Aspects of Xen Functioning
Xen virtualization system combines paravirtualization and hardware virtualization. The first term refers to the adaptation of the existing operating environment to work with Xen. Hardware virtualization, in contrast to paravirtualization, allows emulating of virtual systems with a separate core. This allows you to install any operating system on the created virtual environment. As a result, a slight decrease in the performance of the entire server due to the functioning of the emulation program. However, it also allows you to more flexibly use hardware capabilities and severely limit them to a specific virtual machine. This is optimal for hosting providers that provide services for the registration of dedicated virtual servers.
The merits of the Xen system
- The ability to save resources through paravirtualization.
- Flexible configuration of virtual systems due to emulation.
- The possibility of complete control of the system, namely, the installation of any modules, software environments and add-ons for the virtual machine.
- Hard limitation of hardware capabilities without overselling.
- Reliability and resilience of the system to external failures due to the implementation of different file systems for different virtual machines.
Disadvantages of the Xen system
- Higher cost servers based on Xen virtualization.
- The need to reboot the server after making configuration changes.
- A more complex administration scheme and the need to use Xen package utilities.
Additional Xen features
The high degree of adaptation of the system allows you not to waste hardware resources of a computer or server, because of which the virtual machine has the same performance indicators as the physical one with the same hardware characteristics. At the same time, the educated system has the ability to migrate one running virtual machine between physical servers: this is achieved by “freezing” files, after which they can be transferred either to a new physical environment or to a virtual VPS system. Because of this, the flexibility to migrate entire architectures and systems is provided.
The flexibility of the system is also provided by the support of any hardware: most of the Linux system drivers are supported in virtualization technology. At the same time, it is also possible to create reloadable drivers, which is typical for test or evaluation virtual systems.