Introduction

High availability of network services has always been a concern for me. Networks have to operate in a discrete fashion to achieve this goal, requiring many computers have work together to provide a single resulting service. The techniques and procedures involved can drastically vary depending on the nature of the service to provide. I will discuss some details of the Remote Differential Compression technology implemented in Microsoft Windows 2003 and 2008, as well as the new client side support added in Windows Vista.

How it works

To save some time, I will briefly touch on this and reference Microsoft for a more in depth answer. When a user is working on a file and saves the changes, traditional file replication techniques would detect the change (typically through file time stamping) and copy the newly edited file over to the replication target. The problem here is mostly concerned with large files. This means that at every change of a large file, the whole file would have to move across the network again and again. With RDC, the files is broken into segments. If a file is changes, RDC will determine which segments reflect the change and only transfer the changed segments. This dramatically improves the utilization of network bandwidth.

When can I use this

I recently began researching this topic because of the extremely slow login and logout time in a managed windows network. To improve the way Windows manages these tasks, Microsoft included this technology in Windows Vista.

Additional Resources

Microsoft’s Top Reasons to Deploy DFS in Windows Server 2003 R2 (Also supported in Windows Server 2008)
Distributed File System Technology Center
Optimizing File Replication over Limited-Bandwidth Networks using Remote Differential Compression
Windows 2003 DFS (Distributed File System)