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Cons of virtualization

So now that we have covered the benefits of virtualization let’s discuss about potential problems that we might face with the technology.


Potential single point of failure

This is one of the most underestimated topic when companies think their virtualization projects.

With the added complexity of virtualization and the consolidation of resources if one system fails it’s more complex than with traditional systems.

If a storage system went down on a traditional environment only the servers that were accessing the data on the system fails. With virtualization it’s more common that if a storage system fails lots of virtual machines will be gone.

Same applies for networks on a virtualized environment.


Resource contention


As with network traffic congestion, resource contention can occur on a physical node if one virtual server spikes consuming hardware resources. If one of your physical servers start running out of hardware resources like memory or CPU power all the virtual machines that run on it will start to under-perform.


There are several options that will help you solve this like vmware Dynamic Resource Scheduller (DRS) that allows to perform a load balance of the virtual servers.


Increased administrative overhead

This point shouldn’t be taken literally. I believe that is not an increased administrative overhead it’s just the environment went more complex than before with virtualization in place.

Things are easy to manage but when a problem occurs it’s harder to troubleshoot and more experience is required.


Complex administration

With virtualization your IT environment gets more complex and there’s no doubt about it. It’s because you need to start using advanced servers, storage and networks.

Also the configuration of the environment gets complex as you need to start mitigating points of failure, increasing availability and maintaining SLAs.


High initial investment

As showed before you need to use more expensive equipment and provide yourself with licenses for your virtualization environment. Depending on your IT requirements those could be very expensive and you need to address your budget in order to realize if the organisation can afford it.

Also if you the staff is not well trained on the technology a consultancy might be needed as well. 


Training personnel costs

Staff training is as important as the equipment. In order to setup, manage and troubleshoot the virtualization  environment some training is required. Server virtualization involves several technologies so if the IT team of the organization is small and concentrated on a few people those will have to get trained and lots of new knowledge developed.

Some training I believe is required are on the virtualization technology itself, the type of servers that will be used, networks and storage.

Setting up a virtualization environment is not hard if you know what you are doing but it needs to be well setup upfront otherwise troubleshooting or modifying the configuration could be an uphill journey.


Increased network traffic within a single node

The network traffic of the virtualized servers also gets consolidated on a single node or server. Network requirements should be analyzed deeply to avoid network congestions. Several options are in place to reduce potential problems like using faster ports and NIC teaming.

Again, you will need reliable ports on the network side to avoid potential problems. Those ports needs to be, at least, redundant.


Increase mean time between failure

Because of the complexity added to the environment troubleshooting an issue of a virtualization infrastructure takes more time than it used to on a physical environment.

The stack to troubleshoot is taller than on a physical server and should the analysis should be from bottom to top:

  • GuestApplication
  • Guest operative system
  • Virtual machine
  • Virtualization Layer
  • Physical server
  • Networks (ethernet – storage)

If the virtual environment is running vmware technologies vcenter operations improves troubleshooting tasks with practical information that helps IT administrator find the issue and a possible solution.




There are several security points that needs to be covered. Security is very important on a virtual environment because if one host gets compromised several virtual machines could be affected.

  • VM escaping is a process that runs on a virtual machine but allows an attacker to gain control of the host were the vm is running. Check with the vendor of the virtualization solution how to mitigate this.
  • DoS Denial of service in the past some technologies like vmware HA needed external services (DNS servers and default gateway) in order to work properly. If an attacker could configure the IP address of the services on other devices a DoS occurred. Today virtualization technology vendors are working to eliminate this kind of external requirements.
  • Shared resources (hardware) because all the hardware resources are shared among each virtual machine if an attacker gains access to the configuration service it could change some configurations  that will impact on the performance of the vms that runs on that host.

This post belongs to Explain the purpose and applitaton of virtualization technology

IT strategy analyzing ROI for the Green IT initiative

Continuing with the idea of listing every topic of the exam objectives in order to present them as a way to prepare the exam (sort of a personal guide in order to get the certification).

Develop and implement an internal IT strategy analyzing ROI for the Green IT initiative

  • State objectives and goals for implementing Green IT initiatives.
  • Calculate the savings and ROI for Green IT investments
  • Project management for the implementation of green initiatives
  • Identify needs and cost effectiveness of power redundancy on a system that does not require 24/7 use or access
  • Understand full life cycle assessment of environmental impacts of any product and/or solution
  • Calculate and understand the carbon footprint of an organization

This is part of the Policies and Standards domain of the certification.

As said before, this is just a list. As soon as each of the lines gets a blog post it will be linked from here.

Benefits of virtualization

According to the exam objectives we need to cover the benefits of virtualization. This is the part of the exam where I feel more comfortable writing because of my experience working on vmware technologies for 8 years.

So let’s get straight to the points that the exam requires.

Power reduction
Power reduction is on top of the list of the the benefits of virtualization. Consolidating or virtualizing a bunch of old servers on fewer state of the art servers will guarantee us the power reduction and usage.

Old servers are not energy-efficient so if you get out and replace all of those servers from the data center you will notice a power reduction. Also by virtualizing your servers you are saving space on the data center, which will also get a room space save and a reduction on cooling.

Reduced infrastructure cost
Although reduced infrastructure cost appears on the objectives on the exam I do not agree with the idea. Just because you are using fewer servers it doesn’t mean that you are reducing the cost of your infrastructure.

In fact it will get more expensive. To illustrate the idea let’s say that you replace 30 old servers with 4 state of the art, energy-efficient and fancy servers. Because of the complexity and availability requirements for the new servers the network ports for the servers will be more expensive. You are buying less ports but those ports are more expensive than it used to be.

If I have to think about reduced infrastructure cost I’ll prefer to think about reduced infrastructure operation cost.

Centralization of computing resources
In the same direction of reduced infrastructure cost is the centralisation of computing resources. You have less equipment to administer so you can easily centralise those on a smaller space. 

Centralized administration
Virtualization technologies provides central management capabilities that allow administrators get the job done from a single console improving the way they get tasks completed.

On virtualization projects that were well executed the infrastructure that supports the virtualization technology gets implemented upfront. Deployment of servers, networks and storage are setup all together before you can use the technology.

Unlike traditional servers were you can setup one and then other the idea with server consolidation-virtualization is to prepare the environment and then administer it. The idea is clear and traditional but if you want to perform a centralized administration you need to get the environment ready upfront.

Thin client vs. full workstations
With the same effort that you can run servers on virtual machines you can run desktops. This is called virtual desktops or virtual desktop infrastructure depending on the vendor that develops the solution.

With VDI you can chose the technology (the client) that will connect the user to the virtual desktop that he or she needs to use.

Full workstations are traditional desktops, the same that you can find on any workspace. Thin clients on the other hand are dumb terminals with almost no processing power. There are different types of thin clients that will be covered on a different post.

The usage of thin clients introduces some benefits:

  • Reduced Power consumption: not having processing power, moving parts or coolers thin client consumes less energy than traditional workstations.
  • Centralized administration: VDI solutions allow administrators to patch, create and manage desktops from a centralized point.
  • Centralized information: since the information is on the virtual desktops on the data center it can be backed up and guarantee an improved data loss prevention.

Enhanced disaster recovery
Virtual machines are files, not physical hardware. IT administrators can use this as an advantage when preparing a disaster recovery plan.

Most of virtualization technologies are hardware-agnostic allowing virtual machines to run on different types of hardware, so an identical hardware is not required on the recovery site anymore.

Files can be copied, moved and replicated across sites. The same happens for virtual machines which simplifies the design and execution of recovery plans.



Licensing costs
By consolidating servers you can get a reduction on licensing costs. Just because you are moving some servers into fewer you will easily see the reduction of the quantity of licences that you need to run the environment.

This idea applies only on server consolidation. If you think on get some savings on server virtualization you are not going to get it if your virtualization plan only goes on a one to one basis.

Because of the physical servers count is going to be the same on the virtual machines you cannot get rid of any license at all. In order to see some savings on licensing you will also need to consolidate the services on fewer virtual machines.

There are some free virtualization technologies out there but not all of them brings all the benefits listed here. If you plan to get an environment with all the benefits get ready to pay for licenses which are not that cheap as you might think. You should consider this licenses cost before planing a virtualization project.

Faster deployment
Virtualization simplifies and enhances server and desktop deployment. Administrators can have a set of server or desktop templates that can be deployed in minutes if resources are available.

As mentioned before virtual machines are files so the creation of a new server involves the copy of a template and the customization of it which includes the hostname and ip address among others.

Maximize hardware utilization
By consolidating or virtualizing your servers on fewer physical you are maximizing hardware utilisation. Traditionally an average server consumes only 10~20% of it full hardware capacity. 

Virtualization allows a more efficient way to maximize hardware utilization taking the traditional percentage to an 80~90% in most cases.

Reduced power and cooling consumption
Having less servers on your data centers reduces the power and cooling consumption requirements. Also less physical spaces is required.

Virtual desktops also reduces power and cooling consumption. By using thin clients power requirements for desktops get reduced to a 20~30 percent depending on the type of thin client you are using.

Also as less energy is consumed by the desktops less heat is released to the working space so there is a cooling saving there also.

There are some technologies like vmware distributed power management that takes power and cooling reduction to the next level.

This post belongs to Explain the purpose and applitaton of virtualization technology

Techniques and technologies that will enhance Green IT initiatives

Continuing with the idea of listing every topic of the exam objectives in order to present them as a way to prepare the exam (sort of a personal guide in order to get the certification).

Explain different techniques and technologies that will enhance Green IT initiatives 

  • Duplex printing and use lower cost per page network printers
  • Use Terminal Servers
  • Blade servers
  • Use Energy Star rated equipment
  • Use low power NAS (network attached storage) instead of file servers
  • Use Solid State drives
    • Green building infrastructure and renewable energy sources
    • Insulation- Eliminate air leaks in building/rooms
    • Passive Solar and passive cooling, Active solar
    • Heat recovery ventilation
    • Fluorescent lighting and compact florescent lamps
    • HVAC scheduling and monitoring
    • Smart light switches
    • Proper spacing for cooling IT equipment
    • Solar panels
    • Wind power
    • Other energy sources
    • Heat exchangers
    • Rechargeable batteries
  • Decrease print margins (increase print area)
  • Paperless documents / electronic records
  • Online collaboration technologies
  • KVM switches to share a single PC or a single monitor
  • Measurement of energy for IT hardware and infrastructure
    • Active accountability and management to measure 6-12 months
    • Measure each workstation’s power draw

This is part of the Green IT Technologies and Techniques domain of the certification.

As said before, this is just a list. As soon as each of the lines gets a blog post it will be linked from here.

Server consolidation – virtualization

Server Consolidation
Even though Server Consolidation has it’s own meaning for the objective of the exam has a completely different point of view. Don’t believe that server consolidation is the same as server consolidation but have to recognise that both share the same goals.

In old days when you work on a server consolidation project the main idea was to take some servers that run similar services and consolidate them on fewer. The idea of server consolidation was to reduce space, energy consumption and operative costs.

By reducing the amount of servers in the data center there were less energy consumption, less heat so less energy required to refrigerate the environment. Also as fewer servers were in place less people were required to manage those. But, and always there is a but, it didn’t have the advantages of server virtualization.

Server virtualization
With almost 15 years of experience in different IT fields as technical support, windows administrator, Microsoft consultant and vmware consultant among others I can say that since vmware appeared the day to day work changed drastically.

Why? because the benefits that server virtualization introduced simplified the way we design, operate and manage IT.

In essence the idea behind server virtualization is the same of server consolidation but with some differences. Basically server virtualization let’s you run several virtual servers (virtual machines) inside one big physical server but keeping independence of the operative systems that run inside the virtual machines.

For example with server consolidation if we had eight file servers we would consolidate those servers on four. But, those four servers would be running the same operative system because on a server consolidation project you always tried to standardise the operative system.

Instead, on server virtualization you keep the original operative system inside the virtual machine and, if you want, you could make a virtual copy of the original physical servers on the vm using a process called Physicall to Virtual or P2V.


server virtualization


Depending of the type of server virtualization that you chose there are independency between the virtual machines that run on the physical server. With that if the operative system that runs on one virtual machines crashes the others remain working properly without being affected.

In order to add some vocabulary that is important server virtualization here is a list of common terms that you need to know:

Hypervisor: Is the “engine” (software) that allows the virtual machines. Depending on the type of virtualization that you are using the hypervisor can run on top of an existing operative (Windows or Linux for x86 systems) system or directly on top of the hardware. Running a hypervisor on top of an operative system is no longer in use on new deployments.
Host: is the physical server where the hypervisor is installed.
Guest: is the operative system that runs inside the virtual machine. 

Of course that there are some cons on server virtualization but those will be addressed on another post.

Types of server virtualization

A few different types of server virtualization exists today, each and everyone has it’s advantages and disadvantages. It would depend on your needs which one is the best for your environment.

The most common types of server virtualization are:

  • Full virtualization
  • Hardware-assisted virtualization
  • Paravirtualization

Full virtualization
In full virtualization the guest operative system runs unmodified on the virtual machine and every virtual machines is isolated from each other. An example of Full virtualization is vmware server.   

Hardware-assisted virtualization
This technology first appeared on 2006 with the introduction of Intel Virtualization Technology (VT-x) and AMD-v from AMD that allowed the controller of virtual machines to run below ring 0. these technologies allowed applications to trap sensitive and privileged  calls directly to the hypervisor removing the need of using binary translation (Full virtualization) and Para virtualization.  An exaplme of Hardware-assited virtualization is vmware ESXi.

OS-assisted or Paravirtualization

On Paravirtualization the guest operative systems needs to me modified in order to replace non-virtualizable instructions with hypercalls that communicate directly to the virtualizaton layer.

Paravirtualization is different from full virtualization, where the unmodified OS does not know it is virtualized and sensitive OS calls are trapped using binary translation. The value proposition of paravirtualization is in lower virtualization overhead, but the performance advantage of paravirtualization over full
virtualization can vary greatly depending on the workload.

For more information about the different types of virtualization please check Understanding Full Virtualization, Paravirtualization, andHardwareAssist  

Server consolidation – virtualization belongs to Explain the purpose and application of virtualization technology  domain of Comptia Green IT Certification.

Purpose and application of virtualization technology

Continuing with the idea of listing every topic of the exam objectives in order to present them as a way to prepare the exam (sort of a personal guide in order to get the certification).

Explain the purpose and application of virtualization technology 

  • VDI – Virtual Desktop Infrastructure
  • Virtual Lab
    • On demand Labs and On Demand Applications
  • Server consolidation
  • Storage virtualization
  • Application virtualization
  • Best practices
  • Pros and Cons of virtualization



  • Potential single point of failure
  • Increased administrative overhead
  • More complex administration
  • High initial investment
  • Training personnel costs
  • Increased network traffic within a single node
  • Resource contention
  • Increase mean time between failure
  • Security
    • Concerns from shared hardware, shared resources, DOS
    • Concerns from timing/interrupt attacks (Encryption) and VM escaping

This is part of the Green IT Technologies and Techniques domain of the certification.
As said before, this is just a list. As soon as each of the lines gets a blog post it will be linked from here.

Environmentally sound techniques to preserve power

Continuing with the idea of listing every topic of the exam objectives in order to present them as a way to prepare the exam (sort of a personal guide in order to get the certification).

Identify and implement environmentally sound techniques to preserve power.

  • Power management (Power saving features)
    • BIOS settings
      • ACPI
      • Screen brightness
      • Power saving profile
      • Wake on LAN
      • CPU states
        • SpeedStep™(Intel processors)
        • PowerNow!/Cool’n’Quiet™(AMD)
        • LongHaul™ (Via CPU)
        • LongRun™ (Transmeta)
      • Fan speeds
      • Power on and power off timers
    • OS settings
      • Automatic standby after a specified time limit of non-use
      • Hard disk power down time
      • Wireless and Wired NIC power saving settings
      • Sleep, standby, hibernate modes
      • USB Suspend settings
      • PCI Express power management
      • Search and Indexing power saving mode
      • Windows Vista DreamScene™ power setting modes
      • Multimedia Power settings
      • Power utility in control panel
    • IT policy and procedures
      • Shutdown/power off procedures/policies at end of day
      • Shutdown scripts
      • Group policy
    • Consolidation of office equipment
      • Multifunctional devices
      • Power management PCs and lower power servers replace large desktops with energy efficient laptops and thin clients
      • Consolidation of vendors and/or orders to reduce shipping
    • Reduce graphic card performance to minimum requirements
      • Motherboard video output using low 3D performance or power
      • Select GPU based on average wattage or performance/watt
    • No video card – use of shared terminals and thin clients
    • LED monitors and LED lights
    • Use Power over Ethernet (PoE)
    • Wireless AP Auto Transmit Power or Manual Transmit Power
    • Light/power timer on routers and/or networking equipment
    • Active cooling (water or fan) vs. Passive (heatsink only)

This is part of the Green IT Technologies and Techniques domain of the certification.

As said before, this is just a list. As soon as each of the lines gets a blog post it will be linked from here.

Techniques to dispose of hazardous materials

Continuing with the idea of listing every topic of the exam objectives in order to present them as a way to prepare the exam (sort of a personal guide in order to get the certification).

Implement environmentally sound techniques to dispose of hazardous materials

Environmentally hazardous substance disposal

  • Battery disposal

  • CRT disposal-replace with LCDs

  • General Recycling

    • Recycling of computers for reuse or parts

  • Toner disposal / ink cartridge recycling

  • Cleaning supply disposal

  • Materials that meet RoHS guidelines

  • Retired equipment disposal

  • Use of third party approved vendors for disposal

    • Shredding

    • Incinerating

    • Hard drive wiping

This is part of the Green IT Technologies and Techniques domain of the certification.

As said before, this is just a list. As soon as each of the lines gets a blog post it will be linked from here.

About Comptia’s Green IT Exam Part 3

On the third post about Comptia’s Green IT Certification Objectives I’m going to list the Standards and Policies that needs to be met.

So far I have listed the details of the exam as an introduction and the Techniques and Technologies so now is time to cover the Standard and Policies that Comptia evaluates during the Green IT Exam.

Green IT Policies and Standards 

  • Develop and implement an internal IT strategy analyzing ROI for the Green IT initiative
  • Identify Green IT framework assessment tools, organizations, and standards
  • Identify methods to reduce workforce environmental impacts. 

Each and every topic of the exam will be explained on different posts series but in case you need to get the complete list of objectives of the exam you can get it from Comptia’s web site.

Nicolás Solop

About Comptia’s Green IT Exam Part 2

As stated on a previous post this is the second part of the objectives that needs to be achieved in order to get Comptia Green ITComptia’s Green IT Certification. In this case I’m going to list Green IT Techniques and Technologies that appears on the official Comptia’s Green IT certification site.

Green IT Techniques and Technologies

    Implement environmentally sound techniques to dispose of hazardous materials.

    Identify and implement environmentally sound techniques to preserve power.

    Explain the purpose and application of virtualization technology.

    Explain different techniques and technologies that will enhance Green IT initiatives

Each one of the lines on the list will have it’s own blog post in order to list the details included.

The third part of the objectives will cover Green IT Policies and Standards.

In case you need to check the details of the exam you can check this link.

Nicolas Solop