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Virtualization is a great innovation in technology world and having plenty of advantages, no doubt in that. Meanwhile there are few disadvantages also exist and should be considered. For long time I wanted to publish an article with gathered details from other blogs and with my working experience on disadvantages of virtualization. Disadvantages are very less compared to advantages in virtualization, but still it should be taken care while implementing in production environment.

This list is mainly going with server virtualization. Desktop virtualization in your physical computer or testing environment is not very critical since it doesn’t have high important servers. But, when it comes to server virtualization in production environment with high critical servers, then you must consider the disadvantages also.

 

List of Virtualization Disadvantages

 

1) High Risk in Physical fault

It is great to host/run your very important five servers (as virtual) in one physical server. But, have you anytime imagined impact of these five servers by the single hardware failure in physical server?, it will put your all five important servers offline. Its definitely a big disadvantage and drawback in virtualization which must be considered in production environment while planning.

Yes, you can go with two physical servers with similar configuration and a centralized storage (Network Access Storage – NAS) to run these five virtual servers in cluster environment where single physical server failure will not impact the virtual servers. But, it involves in high cost and slight risk in centralized storage, two physical servers and smooth live server migration (which clustering should do automatically) in this setup.

The cost involves in buying one more similar powerful server, network storage (NAS) and setting up them may be same as buying low end five physical servers which can be run independently.

For example, the above server setup is the real world example where I’m working. In fact, these two servers are hosting 15 virtual servers now. Hyper-v server virtualization software is running in cluster environment and these two servers are accessing a centralized storage. Therefore, if one physical server goes down for any reasons, the second server will take care of the all 15 servers.

But the issue is, these two servers are running next to next in one server chassis. If this chassis or power supply goes down, then the both physical servers with 15 virtual servers will go down at the same time.

It is a high risk of safety also, for example, if this rack or server gets fire (hope it will not),then these all 15 servers can’t be accessible. Luckily we have backup in storage, but it will take some time to restore in different hardware and start the servers.

This is just an example and may not be the same scenario for you. I’m just illustrating to show the high risk in physical server fault.

 

2) Is Performance Same?

I always have doubt in this fact. Let’s say that you have allocated 4GB RAM and 2 virtual CPUs of 3GHz to a virtual server which will be used as a web server in your office. My question is, will the server and application perform like running in a physical server with 4GB RAM and 2 CPUs of 3GHz?, I doubt on that.

Because I don’t think that virtual environment (the layer) fully supports the Operating Systems and applications to talk to physical hardware recourses like how it works in physical servers. I’m not a virtualization architecture expert to understand the real technology, but I assume this.

There will be some certain performance drawbacks in virtual environment compared to similar hardware in physical environment. You must consider this factor while planning and allocating virtual servers.

 

3) It’s not Easy – Complicated

Yes, setting up and managing virtual environment with high critical servers in a production environment is not easy as managing physical servers. If you are expert in PC hardware, then you should be able to manage most of the server hardware and configuration aspects in Intel based servers. Unfortunately, that will not be the case in virtual environment. You must have special knowledge in VMware, Hyper-v  or Xen server virtualization software to work with them.

You would find the similar setup in most of the physical server brands such as Dell, HP..etc. But, the server virtualization software like VMware, Hyper-v Xen are totally different software and you can’t work with all in same knowledge. Special skills and knowledge are required to work with server virtualization products.

 

4) Not Supported by All Applications

Some of the core applications including few database applications are not ready for virtualization ye. Sometimes your applications or Operating Systems may face issues and act differently on virtual environment without giving any clues.

You must consider this while planning your server Operating Systems and application implementation, make sure its certified and supported to virtualization 100%.

 

These are the simple and understandable disadvantages in virtualization. Find out more points indisadvantages of virtualization here in different blog.

If you are an IT person who is deciding virtualization as a solution for your production environment, then its always better to consider disadvantages. Virtualization have few limitations which can’t be managed by you or your company, in this case, physical separate server is the best solution. Whats your opinion?