Advantages, disadvantages and, security of server virtualization

Virtual machines can be used to create operating systems, or environments with limited resources, bring back a proper schedule, ensuring resource.
1. Advantages

The virtual machine can provide a virtual image of your hardware or hardware configuration that you do not have (such as a SCSI device, multiprocessor, ...). Virtualization can also be used to simulate network or standalone computer.
Virtual machines can be used to run multiple operating systems at the same time: different versions or even different operating systems.
The virtual machine allows for robust error correction mechanism and performance monitoring. You can put on some tools such as virtual machine monitor (VMM). The operating system can fix this without loss of performance, or set the script more complicated fixes.
Virtual machines can be separated from what it runs, so it can prevent omissions and errors. You can proactively set an error on software to study sequential processing of it.
Virtual machine software makes the move easier, so the help application and mobile system.
A virtual machine is a great tool for testing the theory. Since they provide isolation, they can work more safely. They packed the entire state of the system is running: the user can save the status, survey it, modify it, reloaded it and etc.
Virtualization can initialize the operating system available to run on the memory multiprocessor shared.
Virtual machines can be used to create the test script is arbitrary, and can lead to some very innovative ideas, quality, efficient.
Virtualization can create these tasks as system migration, backup, recovery & management easy, more convenient.
2. Disadvantages
Virtualization solutions have problems node (single point of failure): the biggest drawback of virtualization is that it has a problem node. When a machine, on which, all running virtualization solutions, trouble or when the virtualization solution of problems, will do crash everything. This sounds scary but the reality of this risk is relatively easy. Increased capacity and frequent backups of the virtual operating system (along with the virtual applications) is a way to help minimize the risk of data loss and downtime due to a single point of failure.
Virtualization requires powerful machines: virtualization can save money because it requires less hardware and this allows limiting the number of physical machines in a business but it does not mean that there is the possibility to use the ancient computers to run virtual new fire solutions. The virtualization solution requires a really powerful machine. If the machine is used is not strong enough, can still deploy virtualization solutions but without strong enough CPU and RAM for them, it will actually interrupt the work.
Virtualization can lead to low performance: even if the machine on which the operating system and the virtual applications are running strong enough, performance issues can occur. One fact that is encountered when running an application on the virtualization environment doesn't work well but experiencing problems when running on system virtualization. For example, the performance of the stress test in the environment has very different results (and wrong) when compared with the stress test on a dedicated machine. The best thing to do when deployed on a virtualization platform is always checked and monitors the underlying issues.
Application virtualization is not always available: while in most cases cannot accurately predict was a specific application can work well when are virtualized or not, there are also some other applications through practices for find When the performance slowdown is virtualization.
Risks of high physical errors: very great to host/run 5 Server (virtual) are important for you in just one physical Server. But you can never imagine the conflict of 5 Server only by hardware in the Server's error in physics? It will put all your important Server 5 in offline status. It is clearly a downside and limited virtualization's great need to consider when planning to set up a server virtualization environment.
3. To resolve the issue.
A problem that we can not disregard that and the risk of service interruption. Virtualization very good, very professional, but its work philosophy is "dump all your eggs in one basket" – the result is when the entire adventure Server mission-critical services on a single Server. Especially when this single Server due to too many downloads the tasks should always be in Active status at full capacity, this will increase the risk of sudden incidents on the physical Server. Once the incident has occurred on the Virtual Server physical Server is on it will also fate.
However, this disadvantage can be solved by a physical Server backup. When the main physical Server to stop functioning due to failure or maintenance, Server backup physical virtual machines that will run the main physical Server to be processed. But to get this feature, will have to incur the cost.
4. Security issues.
The last obstacle is the virtualization security. Running multiple virtual machines on a single hardware issue system, we will be faced with the risk of breaking. For example, in the case of XP mode of Windows 7, we will be faced with the risk of encountering offensive style guest-to-host attack: The attack will attack guest OS, then it will be based on the security vulnerability of the virtualization software to overcome the mechanisms protection, to write to the memory of the host OS. Of course, the opposite case can also occur (attack host OS before then attacked the guest OS).