Virtualization Concerns

In two recent posts (Sustaining the Unsustainable, Towards a New Paradigm) I laid out the case for a new networking paradigm based on ‘virtualizing’ as much of our technology infrastructure as possible.

As I pointed out previously, a simplistic explanation of ‘virtualization’ is that we remove the software applications that now reside on individual hard drives and install them on centralized file servers. When a student or teacher uses a piece of software, it is not running on their individual workstation, it is running on a file server; thus their workstation is a ‘virtual’ one.

There are many benefits to ‘virtualizing’ workstations (see Towards a New Paradigm); but today I wanted to focus on the challenges that we face when setting out to ‘virtualize’ our networks.

1. More servers…
In this new paradigm, we run our software on servers and not on individual hard drives, thus we need more servers. In the current environment the file server is primarily a storage device. One server can service more than 150 workstations. In our new environment we may assign a server to every 30-50 workstations. Because these servers are actually using processing power and RAM to run educational software applications, we want to be careful not to oversubscribe them because doing so will affect application performance. Using a 500 workstation environment as an example, might require approximately (10) application servers.

2. Reliable networking infrastructure…
In the current environment most of the action takes place at the local workstation, and other than Internet use, the network itself is primarily used to store or retrieve files. In the new environment the network is used constantly because the software running on the servers is communicating with the local workstation. In fact, every mouse click and keyboard stroke is sent over the network. In order to create a seamless experience for the user, the network needs to be sound and reliable. The greater the network speeds the better. Typically, we’re talking about 100mbs to the desktop and a gig backbone.

3. High Speed and reliable WAN infrastructure…

If we decide to gather the application file servers into a centralized server farm, then the Wide Area Network needs to be robust and reliable.

Heidi Has Gable comments:

“In a virtualized world, you rely heavily on your WAN connection. Now, if your Internet is slow or even down, you can’t do anything with the computers! If your apps are running locally, at least you could work on the local machine until the Internet circuit gets fixed! I could write in Word, do mind-maps in Inspiration, etc…”

What Heidi observes is partially correct. In a virtualized world when your connection to the server farm is gone so is your ability to use the software that is on the servers. This has nothing to do with the Internet connection. If the Internet is down, you are still able to work, as long as your local connection to the server farm is up.

Some schools mitigate the chances of losing their connection to the application servers by abandoning the “server farm” and deploying their application servers locally in the buildings with the workstations they are serving. By eliminating the WAN they are eliminating a potential point of failure. However, there is no doubt, the most efficient and cost effective deployment is to locate all application servers in a single server farm located centrally somewhere in the district.

Another strategy to combat the worst-case scenario of losing the connection to the application server farm is to put a single application server in each building as an emergency back up. 98% of the time the workstations in the building are using the ‘application server farm’ ; but if the connection to the ‘farm’ goes down, the school building can temporarily log on to the local application server and work until the ‘server farm’ is back online again.

4. Hybrid environments…
One of the most frequently asked question is how does a ‘virtualized’ network handle large multimedia files, Photo Shop, AutoCad, movie making, digital story telling, and high end Adobe applications?

The key to remember is that we can create hybrid environments. Virtualization is not an ‘all or nothing’ proposition. If we have labs or workstations that do ‘high-end’, processor heavy applications, then it makes sense to load and run that specific software locally as we do today.

But a great advantage of software ‘virtualization’ is that even if the PhotoShop software is stored and run locally, we can also install a number of copies of the software on the application servers in the ‘farm’, so that when students go home they can continue to work on the application when they log in remotely.

Hybrid environments can also apply to the hardware employed in the virtualization paradigm. It’s not uncommon for folks to equate virtualization with thin client technology because it lends itself so well to a diskless hardware environment; but realistically, the most common and effective method of virtualizing a network infrastructure is to create a hybrid of older, existing computers with hard drives, thin clients where they make sense, laptops and smaller devices like the Asus Eee.

I will examine several other concerns and the costs of virtualization in a future post.



6 thoughts on “Virtualization Concerns

  1. Hi Pete,

    I can see that my assumption was that there would be a centralized server farm – in which case the WAN stability has a major impact.

    You’re right that if application servers are located at each school then there is a very low risk of lost productivity due to program inaccessiblity. I can see this being cost-justifiable at secondary schools, where there is a larger concentration of workstations.

    At elementary schools, however, it’s going to get pretty expensive to locate a server at each one. I think that starts to impact the business case for virtualization if you have to support every site’s server, rather than have one farm.

    Would you have to upgrade applications on each server individually? I wonder if Windows Server 2008 version of Terminal Services allows Citrix-like functionality of upgrading an application once on a server farm – where the farm is spread across multiple locations?

    Something to reseach…

    I look forward to seeing your examination of costs. It’s a great technical model – it would come down to how to cost justify it, wouldn’t it?

    By the way – have you seen the new HP 2133? I just saw a demo model & it’s looking pretty slick. It’s along the lines of the ASUS, but has a 95% size keyboard (so easier to type on with adult hands) and comes in either Linux or Vista capable models. I think lots of business people and bloggers are going to buy this one!

    Take care,

  2. Heidi,
    The infrastructure that is in place now pretty much works. It takes a lot of effort; but we are holding it together fairly well. I think the foundation of the business case going forward is the desire to move to much more access for students, both in school and at home.

    If we take a 1,200 machine school district and go to a ‘one to one’ scenario over a 5 year time frame, we will be supporting 4,800-5,000 computers. Using the current ‘distributed’ model, this would be an expensive nightmare.

    It would also be difficult to imagine getting to a ‘one to one’ without moving to the Asus, HP, XO, low cost, diskless, mobile devices; in which case we’d want as much software as possible stored centrally.

    I think your point about the WAN is accurate. Distributing application servers in buildings is not optimum. It’s best to have server farms. Something to think about…as time goes on, more and more software is becoming web-based anyway. It’s easy to envision a time when most of our software is coming from somewhere other than the hard drive of our workstation.

    Let’s keep the conversation going.


  3. Hi again,

    About your discussion of hybrid solutions:
    With the schools you’re working with, are they content with having only certain machine capable of running the movie making type apps?

    What I’ve been hearing during my tech planning meetings is that they feel it’s necessary to have movie making, etc… type apps on ALL workstations in a school, as digital storytelling is a key tool for integration.

    I’ve tried a couple of the web tools for movie making or comicstrip creation, etc…
    1. haven’t found the performance that great yet – lots of waiting.
    2. they require students sign up for accounts and Districts are wary of student names/info on external servers.

    What’s your experience?


  4. The general experience has been that graphic heavy apps such as movie making, photo shop, etc need to be workstation specific. Even with 1GB to the desktop and 720 backplane speeds, the processing power on the server would need to be intense to support movie making. I agree with Pete that the hybrid model is the way to go from a managment point of veiw. What gets tricky is that if you need to have a workstation beefy enough to support high graphics, it could certainly support office and web applications without the need for VM ware.

    I envision the 1:1 initiative will be a wireless one using virtualization. I have seen a few potentional student machine models out there but they don’t support the heavy graphic apps. – The choice as we have seen before is portability Vs power.

  5. As a person who works for Dell I think your article about Virtualization is very helpful. There are a lot of things that needs to be considered like capacity planning, management, hardware invertment and also support systems.

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