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{mospagebreak toctitle=Introduction, Options}

Virtualization logos


By now, you've probably heard of virtualization technology. VMware, a virtual software provider, had a very successful IPO earlier this year, and there has been other high profile market activity, such as Dell's $1.4B acquisition of Equal Logic, a virtual storage company. Virtualization is really a hotbed of development and growth, with industry analysis indicating that most IT departments either have or will undertake virtualization projects within the next year.

The concept of virtualization has been around for some time, but in the last few years, has really grown in application and utility, even for the small network. Simply put, virtualization is the ability to pool computing resources such as CPUs, memory, disk space and network interfaces for multiple functions, instead of the traditional 1-1 mapping of hardware to operating system functionality.

Quoting a white paper from a virtualization-focused website, "a single eight-core host will easily accommodate 32 virtual machines on average, which is more than enough to build a complete data center for many small businesses." For a single core CPU, running a host OS and three virtual machines is quite possible.

In this article, I'm going to leverage free virtualization software for both a Linux-based VoIP application and a FreeBSD Storage application. I'm going to use an older Windows XP Pro machine with a 3.2E P4 CPU and 2 GB of DDR400 RAM.

Virtualization Options

One of the cool things about virtualization technology is that most virtualization companies offer free full or trial versions of their software. For a network administrator looking to evaluate options, this can be a useful, low-risk means of determining if and how virtualization can be of value in your network. For long term use, businesses typically require supported and licensed software, but the free versions can be useful for getting started, and certainly valuable in lab environments.

Virtualization companies make money by selling advanced software that works with the underlying virtualization software. VMware offers products like Vmotion that enable centralized management and other features, such as moving a virtual machine from one server to another in real time and without service interruption. This can be highly useful for multiple purposes, including peak demand management, redundancy, and maintenance.

VMware is one of the more well known providers of virtualization software, with solutions for desktop, server, and data center management. VMware Player is the free version for desktop PCs, and VMware Server is the free version for servers, as shown in Figure 1. VMware Fusion is a virtualization product for running Windows on a Mac.

VMware Server webpage
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Figure 1: Webpage for VMware Server

A key difference between the Server and Player is the Server version allows for installing an operating system from scratch and creating a virtual machine, while the Player version will run a previously created virtual machine. For experimenting with various operating systems and applications, the Player version is probably adequate, especially if you're looking to run multiple OSes on a laptop. The Server version makes more sense when creating and customizing a virtual machine.

Microsoft virtualization software includes their free desktop program, Virtual PC 2007, which enables running multiple OSes on a Windows desktop simultaneously. In addition, Microsoft offers Virtual Server 2005—also free—for server-based virtualization. Further, Microsoft just announced a new product, called Hyper-V, to directly compete with some of VMware's more advanced products.

Citrix is a well known remote access software vendor who has also joined the virtualization game with their recent acquisition of XenSource, makers of products such as XenDesktop and XenServer. Citrix offers a free version called XenServer Express Edition. Virtual Iron is another virtualization vendor. Virtual Iron also has a free version available for download.

Before I start in the installation section, let's clarify a few terms. Host is the term for the computer/OS running VMware, while Guest is the term for the computers/OSes running within VMware. For example, I have a Windows XP Pro computer, which is my Host. I'll be loading VMware server software on this host, and have installed Linux and FreeNAS as virtual machines (VMs). The Linux and FreeNAS VMs are Guests. Keep in mind that sufficient OS licenses are still required, whether the OS is running as the Host or Guest.

How To: VMware Installation

I decided to virtualize an IP PBX and a NAS, as these are both independent functions running on my small network. Without the luxury of excess funds, space, power, and switch ports, I'm always looking for ways to optimize functionality in my network. Prior to this project, I was running separate physical PCs for Linux and Windows XP Pro, two NAS devices, and had daisy-chained multiple desktop switches to connect all my devices on a LAN. Each of these devices produces fan noise and heat, contributes to a higher electrical bill, and fills up shelf space in my lab.

I chose VMware's free server software, version 1.3, as VMware seems to have the most buzz in the industry. I tried upgrading to versions 1.4 as well as the newer 2.0 beta version, but had problems with both and reverted to 1.3, which seemed to be the most stable on my Windows XP Pro system.

Downloading and installing the VMware software is straightforward. The software is available from VMware's website, and installation is point and click. VMware Server is designed to run on a server OS, and during installation on XP Pro warns that some of the features may not be available, as shown in Figure 2. Not to worry; it works on XP Pro.

Server warning
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Figure 2: Warning that VMware Server is designed for server OSes

Further, VMware offers a web interface, which on a Windows box uses Windows IIS (Internet Information Services). So I encountered a warning message (Figure 3) that indicated manual configuration may be required. Note that IIS is not installed by default on XP Pro, but can be added via the Add/Remove Windows Components option in the Add/Remove Programs Control Panel. Since I'm not using the web features of VMware Server for this article, I can ignore these warning messages and not worry about IIS configuration.

IIS warning

Figure 3: Warning that IIS is not installed (default on XP)

A few more clicks on OK and a full reboot, and VMware is installed with an icon in the system tray as well as on the desktop. With the virtualization application installed, we're now ready to install a new guest operating system.

How To: Installing a Virtual Linux Machine

Linux is a highly available operating system that comes in many different "flavors" or distributions. In the past, if you wanted to play around with Linux, you'd install it on an old computer or set it up a dual-boot on an existing system. Or if you were lucky, you might find a "Live CD" version of the desired distro, which ran entirely from the CD.

In the old computer case, there is the luxury of a standalone machine, but the negatives of requiring another switch port, more electricity, and more space. In the dual-boot case, changing to the other OS, such as Linux, requires a reboot, creating a trade-off between two systems. And for the Live CD, the OS disappears when you shut down your system.

With virtualization, Linux can be installed within VMware, and it will function completely as if it were an independent machine, all while the Host OS is functioning normally. The first step is to download an ISO file image of the distribution of your choice. For this example, I downloaded a fresh copy of Ubuntu Linux 7.10 from Ubuntu's website.

To install the virtual machine, there is a simple wizard that guides the process. Clicking New and using the Typical options moves the process along quickly. A subsequent window prompts to check which operating system will be used. In this case, see Figure 4, I chose Linux and selected Ubuntu from the Version drop-down menu.

Select an OS

Figure 4: Selecting Ubuntu Linux as the OS

After giving the machine a name and choosing the directory on my host machine in which to save configuration files, I selected my network option, bridged networking, as shown in Figure 5. Bear with me; I'm going to go into more detail on this subject in a later section in this article called "Networking with VMware."

Networking choices

Figure 5: Network connectivity options for the virtual machine

Installing The OS

The next step in creating the VM is to allocate the disk space within the working directory that will become the virtual disk for the virtual machine. In this case, I allocated 4GB of disk space for this Linux machine. Remember, my Linux machine will have full access to all my network hard drives and resources, and I can always allocate additional disk space based on available disks in my physical host computer.

It takes a few minutes for VMware to create the disk, but fear not, it is not partitioning the disk as it would in a traditional Linux install. Rather, it is allocating disk space for the Linux virtual machine, which can easily be reclaimed in the future if I decide to delete/erase the machine.

One of the nice things here is that there are no worries about partitioning software or goofing up disk drives on the host machine. Simply deleting the virtual file created for the virtual machine's disk erases the configuration and returns the capacity to the host machine.

The virtual machine is now created, but the actual OS has to be loaded within the virtual machine. Here's one of the cooler aspects of testing a new OS through virtualization: burning a boot CD/DVD of the ISO file is unnecessary. Simply pointing the virtual CD drive of the virtual machine at the ISO image of the Linux distribution will allow it to boot as if it were booting a physical machine to a physical CD, as highlighted in Figure 6.

Virtual CD drive

Figure 6: Booting an ISO image from a virtual CD drive

At this point, I'm now installing Linux as I would in a fresh install on a physical machine. Figure 7 shows Ubuntu Linux install options. I'll spare you the details on installing Linux, but the end result is a fully functioning Linux machine running within VMware.

Letting the Ubuntu install set up its network interface using DHCP enables the virtual machine to get an IP address on my network, fully independent of the host machine's IP.

Ubuntu boot CD
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Figure 7: Ubuntu Linux installation options in VMware console

The VMware manual provided a couple of tips to optimize the performance of a virtual machine. I'm using a Pentium 4 CPU with Hyper-threading enabled on my host computer, so I could allocate two processors to my virtual Linux machine. However, the VMware manual indicates that Hyper-threaded CPUs can perform worse when selecting dual CPUs for the virtual machine, so I configured my Linux VM to use only one CPU.

Virtualization can be a memory hog, so the more memory allocated to the virtual machine, the better it will perform. The trick is balancing the amount of memory allocated to each virtual machine without degrading the performance of the Host or other guest machines. Linux installations default to 256MB of memory, which can be increased all the way to the total amount of memory in the Host. VMware recommends consulting each OS's documentation to determine optimal memory allocation. For simple command line Linux use, I left it at the default 256MB setting.

Another performance enhancement is to disable CD drives within the virtual machines. They can always be re-enabled if necessary, so disabling them shouldn't cause a problem. Finally, for Linux, VMware has improved Linux drivers that can be loaded using a package called VMware Tools.

In the bottom left corner of Figure 7, there is a message reminding me to install VMware Tools on my Ubuntu virtual machine. Installing VMware Tools is done with the virtual machine running, through a combination of VMware Server menu selections and Linux file activity. There is a handy step-by-step guide on VMware's website for installing VMware tools.

As stated in the beginning, I was running Linux in order to run an IP PBX based on open source software. The open source software I've been using is Asterisk. We ran an article a little over a year ago on running an embedded Asterisk machine here. In my case, virtualization has eliminated the need for the specialized hardware discussed in last year's article and allows me to run Asterisk on a full-blown Linux machine.

I installed Asterisk on my virtual Linux machine, copied my Asterisk configuration files I had saved on a network drive, and I was passing calls through the virtual machine just as I previously had through my physical machine.

How To: Installing a Virtual NAS

We recently posted an article on some really neat free software to create a full-featured NAS device using older computer hardware, called FreeNAS. After reading that article, I thought about trying the FreeNAS software on my former Linux machine, but then thought, why not virtualize this too?

As discussed in Brandon's article, FreeNAS is an application running on the FreeBSD operating system, stripped down and customized to be a full-featured storage device. In VMware-speak, a combined OS and application solution is often referred to as an "appliance." VMware maintains a website with a wide array of these appliances available for free download, including FreeNAS. Typing "FreeNAS" into the search window brings up several choices

I downloaded the FreeNAS ISO file from VMware's appliance page. I created the virtual machine as I did in the Ubuntu Linux discussion above, this time choosing FreeBSD as the guest OS type. I configured the virtual CD drive to point to the downloaded FreeNAS image and clicked Play to boot up the FreeNAS machine. As shown in Figure 8, the screen shows typical boot up messages within the VMware console window.

FreeNAS boot
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Figure 8: FreeNAS boot message screen in VMware console

In a few short minutes, my FreeNAS appliance was up and available for final configuration. Brandon's article does a really nice job of going through the details of FreeNAS, so I won't duplicate his efforts. Two things to add, though, are the network configuration and allocating more disk space to the Virtual NAS.

FreeNAS uses a command line menu for configurations. To allow the NAS to get an IP address, I simply selected option 2 (see Figure 9, below) which allowed the Virtual Machine to get an IP address from my network DHCP server. I'll be going into this in more detail in the next section.

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Figure 9: Selecting DHCP from the FreeNAS menu

To allocate more disk space to my virtual FreeNAS device, VMware has options to add devices to a virtual machine, which are pretty straightforward. After powering down the virtual machine using the shut down options available within the OS, additional virtual hardware can be added to the virtual machine, as shown in Figure 10.

Add Hardware

Figure 10: VMware Add Hardware Wizard

Choosing the Hard Disk option brings up additional screens, allowing selection of which drive(s) and amount of disk space on that drive is to become storage space on the virtual NAS, or on the virtual Linux machine, as in the Ubuntu example.

Networking with VMware

Virtual machines in VMware are networked in a variety of ways, as displayed previously in Figure 5. Those choices are Bridged, NAT, Host-Only, or Do Not Use Networking. Bridged networking is the most common option, which I used for both my virtual machines.

In this option, the Host NIC is shared with the guest machines, with a virtual NIC created for each guest machine. The VMware software creates a couple of virtual network adapters, which will show up in the network connections of the host machine.

The virtual NIC(s) are bridged to a virtual switch created within VMware. The physical NIC is also bridged to this virtual switch. This "bridge" enables the virtual NIC to connect to the same network as the physical NIC. The virtual machine can be a DHCP client and gain an IP from a DHCP server, just as the physical NIC.

Alternatively, a static IP can be assigned to the virtual machine via the network configuration of the virtual machine's OS. Both scenarios enable a virtual machine to appear as a real physical machine to all other devices on the network. Figure 11 is taken from VMware Server?s manual, and shows the bridged networking layout.

Bridged network
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Figure 11: VMware bridged network diagram

I use the /24 network for my LAN, with my XP Pro machine's IP address being By going into my router, I was able to determine that the Linux virtual machine was assigned and the FreeNAS virtual machine was assigned

From a network perspective, both of these virtual machines are completely independent of the XP Pro Host, with their own IP addresses. Indeed, I can access and ping all three machines simultaneously, even though they are sharing the same physical NIC.

Another VMware networking option is NAT. If the Host computer is directly connected to the Internet, it may not be possible to give the guest computers their own external IP addresses. In this case, VMware can perform as a NAT device, complete with a virtualized DHCP server to issue IP addresses to the guest operating systems? virtual NICs.

The physical NIC is connected to the outside world and then acting as a virtual NAT service. The virtual NAT service is connected to the virtual switch, where the virtual machines' NICs are connected, enabling them to connect to the outside world. Port forwarding can be set up on the virtual NAT device, enabling external devices to talk directly to virtual machines behind the NAT, exactly as with a typical physical gateway router.

In Host-Only network configuration mode, the virtual machines connect to a virtual network, only accessible by the host machine. Routing can be enabled between the host machine and the virtual machine. This is an interesting option if the design calls for running virtual machines on a different subnet than the host machine.

Another networking option is to run the virtual machine entirely within VMware, with no network access at all. This option may be useful in lab environments or for security purposes.


After experimenting with virtualization, some interesting benefits become apparent. There is no BIOS to configure or manage for my virtual machines, as each is running on a common virtual platform. Remote access to a server's BIOS requires additional devices, which are eliminated through the use of virtualization.

Rebooting my virtual machines does not require physically powering devices up/down, but is done completely within the confines of the virtualization application, without affecting the host machine. Since rebooting is done inside the Host, I can watch a machine fully power down and up, and monitor the POST messages via the VMware console.

Interestingly, the virtualization application is not required to keep the guest machines running. Once the guest machines are up, the VMware software can be closed, yet the guests continue to run, with complete functionality, in the background.

The XP Pro machine I used as a Host is running completely headless, meaning it has no keyboard, monitor, or mouse. I access this machine over my network using Remote Desktop. Simultaneously, I can access the virtual Linux machine, which runs on that XP Pro host, using SSH for secure command line operation, or VNC for more user-friendly GUI-based operations. In addition, I access the FreeNAS device via the web configuration pages, as discussed in Brandon's article.

I have run simultaneous connections to all three from my Windows Vista laptop without issue. As shown in Figure 12, all three machines are running at the same time—sharing the same physical hardware.

Simultaneous virtual machines
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Figure 12: The power of virtualization: three virtual machines run simultaneously on one computer

This demonstrates how network technology enhances virtualization. Remote Desktop, SSH, VNC and Web Utilities are all network access technologies and nothing new. But using them with virtualization software produces fully functional devices without the related hardware costs.

When considering virtualization on your network, there are some key metrics to consider that could help quantify the value. Some people estimate that the typical IT server is running at 10–15% of its overall capacity, meaning that a properly configured VMware server can run 5–10 different virtual machines relatively easily.

An article in the Boston Globe (12/14/07), which is a reprint of a Reuters article, quoted a VMware spokesperson as stating, "companies can save about $600 per year and 7000kW hours in electricity for every software application put onto a virtual machine." For my small network, I doubt I'll save $600 virtualizing my little Linux machine and a single-disk NAS. However, if each of my virtualizations saves one-tenth that amount per device, I will have saved $120 in electricity this year.

In this article, I've walked through steps using entirely free software to create a virtual Linux machine to be used as a VoIP server, as well as creating a virtual FreeBSD machine to be used as a virtual NAS for data storage. Both devices function completely as would a standalone physical machine, with their own IP addresses, disk space, and network interface. Through the use of virtualization software, I've saved network ports, electricity, physical space, reduced fan noise and CPU heat output, and even eliminated the need to burn CDs; all things that would make Al Gore proud.

Through my virtual IP PBX, I can make real phone calls, and through my virtual NAS, I can store real data. The question is, do these virtual devices function as well as they would in a standalone configuration? In a follow-up article, we're going to take a look at virtualization's effect on application performance and attempt to answer that exact question.