Disadvantages of Virtualization, What’s Your Opinion?

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.

Disadvantages of Virtualization, server virtualization software

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 in disadvantages 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?

Comments

  1. G says

    HI Dinesh,
    I agree with you for some points which you highlighted. virtualization is not a technology to run the complete production. We could be benefited only if we use that in mix mode. Technically & cost effectively. Also yes , We know we cant run each & every server on a V- environment

    1) Regarding the Risk factor you mentioned, yes there is a risk of falling down the Host , So guests will be down automatically. So depending on the criticality we should split those servers in to different enclosure & Racks. Thats simply Criticality Vs Investment.

    2 Is Performance Same ? – Yes for servers which we do not stress the server , No for high utilization applications . So we should know what we should make online in virtual environment. Eg – Its not a good idea to run production Terminal Server as a V – guest.

    In any technology we have Plus , Minus & good & bads. so we should mix products to get the max output to the production.

  2. Jitendra.K says

    Hi Dinesh Jitendra Here

    I Do Agree there are some disadvantages on virtualization.

    I feel virtualization technology fits more for DTV is (Desktop Top Virtualization).
    For example In an organization where they don’t want to invest more on Desktop Machine, ie If they want to buy 250 desktop there investment is more, In this case virtualization helps them.
    Just they can create vm’s on vmware esx box where all vm’s are stored in san. Just This vm’s are published or Streamed via Citrix DDC. (Desktop delivery Controller). Here on client side there will be no hdd os get booted without hdd, here thin client box are used like which comes from sun or Wyse . Here os and applications are installed in centerlised location and streamed to thinclient box.

    But on server virtualization we need to think more and do more rnd before putting to production environment.

    For Example
    Your Domain controller can’t be virtualized.
    Your Huge Data Base of SQL can’t be virtulized.

  3. says

    I think virtualization is the only way forward when it comes to datacenter management. Agreed, that you need a different set of skills but the benefits far outweigh the drawbacks. As far as performance is concerned, you’re only talking about CPU here, but in my opinion, the bottleneck is modern servers is not the CPU, it is the IO subsystem and as long as your physical server can handle the IO load, everything will be fine.

  4. says

    Hi, I have found your blog when searching how to use physical disk in Virtualbox :P Not the best software for server virtualization but I don’t really have choice (Windows Host).

    Anyway, I read your article about virtualization and it’s very interesting. I have a wonder about the point n°2: Intel VT-x / AMD-V are designed to give “full access to CPU” on a guest, and virtual memory is a cluster of physical memory. So isn’t it possible to have full performance ?