I got a great question into the Ask the Architect email bag that I thought it would be great to share and potentially create a good discussion. Let’s say you are in a classroom setting where students are only in the class for 4 weeks and then after those 4 weeks, you need to reset all desktops back to a base image. Before desktop virtualization, you could use Ghost or other tools. But could we use desktop virtualization for this? Does it make sense?
As this environment is already using the local, physical desktops, I’m assuming the desktops have adequate resources, so let’s continue to use them by using the Streamed VHD FlexCast model. For those unfamiliar with Streamed VHD, I’ve provided a very rough drawing
Because the desktops have enough resources, we want to use those for computing power, thus reducing the need to buy a lot of servers in the data center. All we need is a Provisioning Services server. The classroom image (1 per classroom or 1 for all classrooms) will be streamed across the network to each physical desktop.
The unique thing with this use case is that students need to be able to modify the desktops and then when the 4 weeks class ends, those modifications are thrown away. With Provisioning Services, you simply use the Differential Disks, which will store the changes (write cache or delta disk) on the Provisioning Services server. So the PVS server will be holding the differential disks for all of the classroom desktops.
When the 4 week class is over, you simply remove the differencing disks and the desktops reset to the base state, ready for a new class. Pretty slick.
What do you need to make this work?
- One or two PVS servers (for redundancy) with enough storage to hold the disk image and the differential disks. You will want these disks to be fast as well to reduce latency
- At least 100Mbps switched to each endpoint
- Endpoints that are similar in hardware configuration (the more identical they are, the easier this will be)
- Network boot capabilities on the desktops and configured within the environment (DHCP, PXE, TFTP)
Note: If you want to see how to configure the difference disk or to see it in action, take a look at this CitrixTV Video.