When we first implemented SCVMM into our organization one challenge that was recognized was how to easily manage our remote library shares. With the potential for several remote libraries, it immediately became cumbersome to ensure that each location had all of the new or updated system images.
We immediately began to work on a system to allow us to manage 1 local library share, and have the contents of that mirrored at each remote location. Windows 2003 R2 has a new feature that fit the role perfectly.
Enter Server 2003 R2 DFSR :
For those not familiar with DFSR, it offers a load of potential configurations and uses. The automatic replication and the compression built into it were the main benefits for the library replication.
The compression method used by DFSR is called Remote Differential Compression (RDC), more Here. A cool thing about RDC is that it is optimized for VHD files. A quick scenario of RDC is as follows:
VHD A is a Windows 2003 Server Standard Edition with SP1 and is 5GB
VHD B is a Windows 2003 Server Standard Edition with SP2 and is 5.2GB
RDC breaks the VHDs down into smaller parts and replicates, then the parts are put back together at the remote location. VHD A is replicated first. Once replication of VHD B begins, each part of the file is compared to other file parts that already exist at the remote location. Parts that match are not replicated, but reused from parts existing at the remote site.
This means that VHD A has all 5GB replicated. But only the different parts of VHD B have to be replicated. So we'll say the .2GB is the only data that has to be replicated for VHD B!
Since the majority of our SCVMM library content is VHDs and ISO files, DFSR really yields itself as the perfect companion. We've seen as much as 70-80% reduction in WAN traffic from using DFSR. The main benefit that I like though is I can update an image and place it in our local library, and I know that it will also be available at our remote sites once it is replicated.
Here is a quick diagram of the setup I described above: