Pitfalls of Virtual Desktop Infrastructure

The last couple of months we heard it more and more. VDI. The Virtual Desktop Infrastructure. Many companies see it as the new revolution in flexible working, and yes, VDI adds a lot to what we want. One single image for everyone. Streaming applications to the image or install applications on the VDI image so everyone has them available.

But all the benefits also have their disadvantages. These pitfalls should be detected early in the process to be aware of them. If you find the pitfalls early you can take countermeasures to avoid them.

Most heard problem in VDI:

The image is incredibly slow and users have problems working with the software applications in the image.

This is mainly because we need to give these images more and more memory. But virtual memory is not real memory. It is just a file on a disk. The image can read and write into this file. But the larger the file gets, the slower it goes. So finally you will see that when you give an image more then 512MB of memory the file becomes over a specific size and the image will slow down. To overcome this we just have to add more and more memory, but we will not get a fast machine.

Second problem is the Virtual Network interface card. The Virtual interface card is just a piece of software that uses processor utilization. When we copy or stream a application into the image over this Virtual Network card the processor utilization will rise and rise. Up to 50%.

So how do we get these applications inside this virtual image?

First we have to decide how we want to work.

If we need application installed inside the image we need to configure these and we need to buy licenses for all users. That is because they promised us one golden image. But when we have one golden image it is identical for everybody.

Then we need to determine which applications we copy inside the image and how we distribute them.

After we find out how we distribute them we are going to determine our image and everything we need for it.

In this article we use a company with 1000 users. That is easy for the calculations.

We need 1000 images that will be hosted on our SAN. So first we have to calculate the size of our image.

If we want Windows XP we need about 2 to 2.5GB of space to install and run Windows XP. Then we have to determine the amount of memory. Let's say 1 GB of Virtual memory. This 1 GB needs a page file about 1.5 times the size of the Virtual memory so that will add 1.5GB to our image.

Now we already have 4GB of size. Then we need space for our applications. When we stream the applications inside the image we need to make sure that we have 1.3 times the space to let this work. If we want 15GB of applications inside the image that will add 15GB times 1.3 to our image. We already hat 4GB and now we need 20GB additional. The total size will be 24GB and then we also need some free space. This will bring our image to 25GB in size.

This means we need 25TB of hard disk space on our SAN to facilitate all the images.

Then we need to calculate how many VDI servers we need. VMware and Citrix say that they can facilitate 40 to 50 Images on every server so for 1000 images we need 20 servers to host our images.

In the first instance we know what we need to buy and we can start building our infrastructure. We build the image and we configure Windows XP in our image. Then we install the antivirus solution on the image and the applications that we need.

And then we start packaging our applications.

After we have finished we are going to deploy our golden image for 1000 users.

Then we see our first problem. Deploying an image of 25GB takes about 20 minutes. And then we need to sysprep the image. So after about 20 to 30 minutes the image is ready to go. Don't even think about doing this 1000 times simultaneously. Your SAN will not like it.

After a couple of days when we have 1000 images running we will see another problem. We forgot to count the virtual memory. Nobody pointed to that, but we need 1.2 times the amount of virtual memory on our SAN to host it. This miscalculation brings in the need to add about 1.2TB of additional disk space on our SAN.

But we never mentioned how we get the image on the client. When we use thin clients all the traffic between the image and the thin client will go over the network and that will eventually bring the speed of our network down. So probably we need to upgrade it to a Cat 7 1000GB network. Pretty expensive.

Because of the time it took us to deploy 1000 images we determined that it is easier to manage the 1000 images instead of deploying them every time.

And believe me. We have seen various companies that deploy one golden image and end up with 1000 Virtual Fatclients. There go our benefits.

Are you aware that Symantec has a pretty cool solution for these problems? Yes they have, and that is why I write this article.

We used three Symantec products to build the best, coolest and fastest VDI solution you ever saw.

So let's start what you can do differently so you do not get stuck with 1000 Virtual fatclients.

First we use Nlite to build a very small image. Just throw away all the drivers and add the VMware drivers to it. It will save you more then 1GB of disk storage.

Eventually we built an image that is only 1.2GB in size.

Then we added Symantec Endpoint Protection to it. Symantec Endpoint Protection is the best antivirus solution for VDI because it works fast and brings in baseline analyses into the image. So we can easily remove a contaminated image to another Vlan without compromising the original image.

The second technology we added is Symantec Workspace Virtualization. With the DVS4VDI add-on Symantec Workspace Virtualization will be reading the applications form a centralized disk. So instead of having a FSLRDR directory on every image we share this with all the images.

Managing applications can be easily done just by creating a mapping to this disk. We developed a small tool to map the disk as it was local. Now we can easily add, remove or replace files inside the directory.

The last technology we added is Symantec Workflow.

By creating workflows our users can be made self supporting. We can build a workflow that enables us to activate or de-activate applications, and only those applications that a user has permissions for.

Eventually when we calculate this we get some different numbers.

1000 times 1.2GB is 1.2TB. The image is very fast. We only give it 384MB. DVS4VDI gives you a 800 MB big swap file outside of the image that represents additional memory so our image eventually has 1.2GB of memory available. Then we need to add 450MB of disk space that represents the virtual memory itself.

So eventually we need 2.5TB of disk space. You now saved 24TB of disk space. Instead of 27TB we only use 2.5TB.

Deploying 1000 images of 1.2GB takes a much smaller amount of time then do the same for a 25GB image. We deploy the image in only 59 Seconds. And we can do this 1000 times in less then three hours.

Because we do not copy or stream the software inside the image we needed a different technology to use the centralized repository. Therefore DVS4VDI uses a diskprotocol to map the drive to the image. This also overcomes the problem that Symantec Workspace Virtualization does not work on network drives.

If you are taking a look at VDI, just don't forget adding Symantec software and DVS4VDI. It will save you a lot of time, disk space and money. Now it is time to put your feet on the table and relax while you are fully automated managing thousands of images at one time.

Regards
Erik Westhovens
www.virtualstorm.org