Analysis of VMware Server Virtualization Technology

Analysis of VMware Server Virtualization Technology

Server Virtualization has become one of the hot topics. At present, the leader in the server virtualization market is VMware. In addition, the strength of Microsoft and Citrix cannot be underestimated. Before selecting a server virtualization solution, enterprise users must carefully evaluate their plans. In the field of server virtualization, VMWare is undoubtedly the leader in virtualization applications. Its products account for more than half of the market share. VMware's server virtualization products can be based on Windows, Linux, UNIX, and other platforms, which is incomparable to its competitors, let's take a look at VMware's "town store treasure"-VMware infrastructure3 (vi3 ).

It should be noted that vi3 is not a server virtualization software, but a combination package of server virtualization software, which consists of VMware ESX Server, vmfs (Virtual Machine File System), DRS (Distributed resourced schedced), virtual SMP, VMWare ha (high availibility), VMWare vmotion, protected lidated backup, virtual center and other software components. Here we will introduce VMware ESX Server, VMWare
Vmotion and virtual center components. VMware ESX Server is the core of vi3, while vmotion and virtual cente are the main roles of server virtualization application management. They provide dynamic mobile virtual machines and automatic monitoring of resource availability, the best way to use available computing resources.

VMware ESX Server: Efficient Virtual Machine Creation 

VMware ESX Server adopts semi-virtualization technology, that is, it does not need to be preinstalled with any operating system. Users can directly install VMware ESX Server on bare metal servers, in this way, the server can be divided into several virtual machines, and system resources can be directly and effectively allocated without the need for a "host" operating system. The working principle of VMware ESX Server is to isolate each virtual machine from the server hardware and other virtual machines (figure 1) to ensure that other virtual machines are not affected when a virtual machine crashes. Virtual machines do not disclose data to each other, and applications can only communicate through the configured network connection, VMWare
ESX Server encapsulates the virtual machine environment into a group of files for backup, movement, and replication.

VMware vmotion can transfer a running VM from one host to another

VMware ESX Server separates physical machine resources for use by virtual machines, and even overuses memory, which means that the total memory of virtual machines can safely surpass the actual physical memory of the server, this function improves the overall utilization efficiency of server memory. VMware ESX Server can be installed almost immediately on new servers and maintained on existing servers in use without downtime.

Of course, VMWare ESX Server puts forward higher requirements on enterprise IT personnel in terms of applications. For example, vmfs, which brings performance improvement to the direct control of hardware, is a file system format developed by VMware itself, used to store VM data. Compared with the multi-function file system format provided by the operating system, vmfs provides faster and more reliable reading speed. Unfortunately, virtual machines stored in the vmfs format have to face the tedious and risky format conversion if they want to migrate to other virtual environments. In addition to the migration and transmission difficulties caused by file formats, VMWare ESX Server is still facing the driver problem-VMware ESX Server does not have a hard drive loaded with local SATA interfaces, so Vmware
ESX Server users have to consider using local SCSI interface hard disks or remote storage devices (such as NAS and San ). In addition, there are certain requirements for using VMWare ESX Server. For example, to use VMware ESX server, the server must use intel or amd cpu that supports hardware-assisted virtualization technology, to run the required processor commands.

The biggest advantage of virtualization is server integration, which saves operation costs, but this also means that enterprises need to put all the eggs in one basket, increasing risks. The main problem with server virtualization is single point of failure (spof). In the past, users could run 20 workloads on multiple of their physical servers. When one of the servers goes down, although the situation is terrible, but it does not affect the entire server network, and 20 workloads cannot be stopped. In a virtualized environment, if 20 workloads run on one server, once the physical server goes down, all the workloads will be paralyzed, it is a disaster for enterprises. Vmotion, the real-time migration component in vi3, is considered to be the biggest highlight of this product. This is also an important reason why many enterprise users adopt vi3, this feature allows you to migrate workloads from one physical server to another without being affected by downtime.

Unlike VMware converter's P-V (physical to virtual, physical machine migration to virtual machine) feature, the P-V needs to be shut down to stop the server, to migrate the application load (P-V is mostly used to solve compatibility issues with history programs ). VMware vmotion solves the problem of system reliability. When a virtual machine fails, the administrator can smoothly migrate the virtual machine online to another virtual machine. In this process, the server does not need to be shut down, thus effectively ensuring business continuity. Using VMware vmotion to migrate virtual machines from one physical server to another in real time is achieved through three basic technologies (figure 2 ).

VMware vmotion can transfer a running VM from one host to another

First, the entire state of the VM is encapsulated by a group of files stored in the shared storage. VMware vmotion cluster vmfs allows you to install multiple VMware ESX servers to concurrently access files of the same Virtual Machine Group. Second, the active memory and precise execution status of the virtual machine are quickly transmitted through high-speed networks, allowing the virtual machine to run immediately from the source ESX Server and switch to the target ESX Server. Vmotion continuously tracks memory transactions in the in-place graph to ensure that the user is unaware of this transmission period. Once the entire memory and system status have been copied to the target ESX Server, vmotion stops running the source virtual machine, copy the bitmap to the target ESX Server.
Server, and restore the virtual machine on the target ESX Server. The entire process takes less than two seconds over Ethernet. Finally, the network used by the virtual machine is virtualized by the underlying ESX Server to ensure that the Network identity and network connection of the virtual machine can be retained even after the migration. Vmotion manages virtual MAC addresses during this process. Once the target machine is activated, vmotion will ping the network router to ensure that it knows the new physical location of the virtual MAC address. Because Virtual Machine migration with vmotion can maintain a precise execution status, the network identity and active network connection result in zero downtime and user operations will not be interrupted.

However, there are prerequisites for achieving the above process. Taking VMware ESX as an example, vmotion can take effect only when the following three conditions are met. First, a high availability relationship must be established between ESX servers, the second is to store virtual machine files in the shared disk drive of the local area network, and the last point is to complete the relevant settings on the virtual switch. During the actual migration, only the setting files of the virtual machine are migrated, rather than the Virtual Disk Files of dozens or hundreds of GB. We recommend that you connect each ESX Server to a line of a Gbps or higher level to ensure that there will be no broken lines during the migration process. If the distributed resource in the vi3 component is used together
Schedmotion (DRS) is a vmotion operation. When one of the ESX servers is overloaded, the system can automatically migrate some virtual machines to other physical servers to achieve load balancing.

In addition, before intel releases the VT flexmigration technology, vmotion has constraints that require the two server platforms for migration to adopt the same chipset, that is, different server platforms cannot be migrated online. For example, the two-way server platform cannot be migrated to the multi-channel server virtualization platform. With the technical support of Intel VT flexmigration, the constraints of Virtual Machine migration are broken. Users can freely migrate virtual machines on different Intel Server platforms. It can be said that vmotion leaves the Administrator's worries about putting all the eggs in the same basket.

At ordinary times, a person may be able to manage 15 ~ 20 physical servers, but after virtual machines are deployed, one person can manage 100 or even 200 virtual machines. But how to manage it more conveniently? In fact, the introduction of Virtualization in the data center actually adds a virtualization layer, but it does not increase the difficulty of management. Virtualization management software can manage and control virtual machines, greatly reducing the management complexity of large data centers. For example, VMWare Center is a good example. virtual center provides an intuitive management interface, it provides a wealth of data and data to monitor and integrate the data center, provides a powerful means for the management of virtual machines in the data center, and becomes a necessary tool for the new virtualization data center.

Virtual Center has powerful VM management functions

Virtual Center is a set of virtual architecture management software, as if a logical virtual machine pool, which can manage Virtual Machine resources within the enterprise (Figure 3 ). The Virtual Center interface provides a powerful browsing function that allows you to browse all the virtual resources in the data center. With the virtual center, you can use the single-point console to manage hundreds of servers, so that the chance of hardware downtime is zero. The main advantage of virtual center is that you can use a single console to manage a distributed virtual structure. Of course, this can only reflect the bid value if you have so many servers.

When talking about VMware ESX Server, you have to talk about VMware esxi server. VMware esxi Server is a lite version of VMware ESX Server (Figure 4). It also uses semi-virtualization technology, but it features free use. Although free, VMWare esxi is still an enterprise-class Virtual Machine hypervisor that provides an on-premise host architecture that is close to local performance.

Features of VMware esxi Server

Some functions of VMware ESX Server depend on a Linux operating system called the service console. esxi cancels the service console and reduces the occupied space to less than 32 MB. By canceling the service console, the esxi server completes the transformation from the local command line interface to the remote management tool. The service console is replaced by a remote command line interface that complies with system management standards. These optimizations have greatly improved the efficiency of the esxi server. At the same time, the esxi server has outstanding performance in terms of control and usage. For example, the two physical servers can be integrated into one. However, if you are a large enterprise with dozens or even hundreds of virtual servers and want to quickly migrate workloads in response to change requirements, free esxi is not applicable because ESX
Server components cannot be applied to free esxi server.

VMware esxi is difficult for novice administrators to operate because the service console is canceled due to its simplified functions. For example, without the help of VMware technical support personnel, users cannot use the dropbear SSH client or other technical support modes, this may result in invalid certificates of VMware esxi and damage to the technical support contract.

The production and manufacturing system of Guangxi Yuchai Group needs regular maintenance, but the production system must run continuously, so the maintenance and upgrade time for system management personnel is very limited. In addition, the enterprise's production system needs to regularly deploy some new applications, some of which have a long installation cycle and complex configurations, which is not conducive to the rapid deployment of the system.

In order to ensure the normal operation of enterprises, the management of Yuchai Group has set a very clear goal: enterprises need to quickly test the environment for testing services; enterprises need to change the testing environment in a timely manner, in order to make better use of hardware facilities, it is necessary to quickly migrate obsolete applications to the new environment, and reduce the number of hardware devices to reduce the workload of subsequent maintenance, it also saves device space and data center energy consumption.

In response to this requirement, the Information Department of Yuchai Group decided to adopt VMware's ESX server virtualization solution, using five Dell poweredge 6850 servers (the server uses an Intel server chip ), the backend connects to the EMC cx600 disk array and builds the entire virtualization application architecture. With VMware ESX Server 3.5 and the vmotion and HA functions, virtual environments for some tests are deployed, and 5 to 5 physical servers are deployed ~ The six virtual machines implement fast migration of virtual machines by using the virtual center for unified management of virtual machines and computing resources and storage resources. Using the ESX server virtualization solution, after a system is deployed, a new system can be quickly cloned using its template function, which greatly shortens the server deployment time.

It took several days to prepare the test environment. Now, with the server virtualization template, it takes less than one hour to complete the preparation. If the previous environment was reused, you only need to enable the Virtual Machine in several minutes. After the application server virtualization solution, the server utilization rate has increased from the original average of 10% to the current 70% ~ 80%. Previously, if there were more than 10 test tasks at the same time, because multiple departments were involved, each task required multiple servers and dozens of servers had to be prepared at the same time. After the ESX server virtualization solution is adopted, it is split on a server with strong hardware capabilities to quickly build the required test environment and reduce the number of servers and storage devices, at the same time, it also reduces the consumption of data center space and energy consumption costs.