Virtual Desktops - It's all about the implementation
Posted by Pete Sorensen on Fri, Sep 25, 2009 @ 03:45 PM
VDI is a very useful concept that is starting to take hold in production desktop environments. In essence it is virtualizing desktop Operating Systems, Applications, and Data and moving it all to the data center with the user only accessing these resources via endpoint. This endpoint can be a thin/thick client or web browser and in some cases a smart phone. The idea is that the endpoint is stateless and ideally retains no user data as it only serves as an I/O conduit.
VDI like most concepts is quite broad. However I tend to view it this way:
As you can see the Operating System, Application layer and User Data are treated as separate and independent entities which align to give the user a seamless experience. This allows for easy modification of each layer without impacting the others. With this model the O.S. is just a stateless environment for applications to be launched and data to be generated and modified. But if the O.S. were to disappear, the applications and the user's data would not be affected. A new O.S. could then be provisioned for that user with a minimal outage.
On the application virtualization side, applications would launch from ‘file servers' and be managed by application virtualization technology such as InstallFree, App-V, and ThinApp. The advantage to this is if you want to push an updated version of an application to a user set you would virtualize that update and push it to the file server. Then the next time the user runs this application they would be running the new code. Inversely if you wanted to serve multiple versions of an application simultaneously this would also be supported as the applications would each be in their own virtual space on the O.S. they are executing on.
User data is a matter of re-direction to CIFS file servers (for windows clients). This means actual backups, snapshots and dedupe of user critical data is made accomplishable in an efficient and cost effective way. This also brings tiered storage into view. Having your actual VM's on low latency, high throughput storage (SAN) and your raw data on cheaper, higher density storage (NAS). This is an important cost savings element.
Endpoints do not have to be consistent over an environment. Repurposing Thick Clients, using various Thin Clients or just a web browser are all acceptable. There are a few things to consider with endpoints such as multimedia performance, USB redirection, VPN capability, Connection Broker compatibility and security being the ones that are of main concern.
VDI does a great job of taking the risk and load off of desktops; however it redistributes that load to your network infrastructure. You must look long and hard at your network to verify it is able to keep up with the increase and type of traffic. VDI traffic tends to be bursty as is the nature with remote display protocols. It is also sensitive to latency and packet loss which is a strong consideration on WAN deployments on the fringes of you network. VLANs and QoS are good measures to implement to keep this traffic segregated and at the right priority level. Redundancy for these systems and the networks they run on is key, as any outage affects many users simultaneously.
So the conclusion is that VDI's benefits are a great for cost savings, increasing quality, and managing your desktop infrastructure. It provides enhanced reliability, usability and security to your infrastructure. However implementation must be well thought out and engineered from the NICs to your storage and to the end points. Implementation in phases is a good practice as it allows you to ramp up your SA's skills and find trouble spots without large impacts.