Windows Storage Server 2012 R2 — Improved DFS Replication

Hi Folks -

My list of Top 10 Features in Windows Storage Server 2012 R2 included DFS Replication. In this post, I’ll take a closer look at the enhancements we made to DFS Replication and how you can benefit from them.

DFS Replication (DFS-R) is a service in the File and Storage Services role. It provides a means of efficiently replicating folders—including those referred to by a DFS namespace path—across multiple servers and sites. DFS-R uses an algorithm called remote differential compression (RDC), which detects changes to the data inside a file and enables DFS Replication to replicate only the changed file blocks instead of the entire file.

New capabilities related to DFS Replication in Windows Server 2012 R2 and Windows Storage Server 2012 R2 include:

  • Massive Scale improvements! Want to replicate 100TB of data? Now you can! DFS has been limited to supporting about 10TB of data since Windows Server 2003. With Windows Storage Server 2012 R2, we have tested end-to-end deployments that have over 100TB of data. Remember that there are a lot of factors to successful replication and your environment may not support a huge dataset like that, but it’s great to have confidence that very large replication sets are possible. If you are planning to replicate a really big dataset over a slow WAN, then I would probably get a suitcase and take the first copy over by hand.

  • Windows PowerShell module for DFS Replication, which provides cmdlets for the majority of administration tasks for DFS Replication. You can use the cmdlets to perform tasks such as creating, modifying, and removing replication settings, as well as for the new functionality in R2, such as database cloning and preserved-file restoration. You can now automate all of these tasks by using PowerShell!

  • Database cloning for initial sync, which provides support for bypassing initial replication when creating new replicated folders, replacing servers, or recovering from a disaster. You can export a DFS Replication database from a volume on one server, and then pre-seed replicated files and import the database on multiple servers. This can reduce initial setup times by up to 99 percent!

  • Database corruption recovery, which provides support for rebuilding corrupt databases without unexpected data loss caused by non-authoritative initial sync. When DFS Replication detects database corruption, it rebuilds the database and then resumes replication normally, with no files arbitrarily losing conflicts. When replicating with a read-only partner, DFS Replication resumes replication without waiting indefinitely for an administrator to manually set the primary flag.

  • DFS Replication WMI provider, which provides the latest Windows Management Infrastructure (WMI)-based methods to programmatically manage DFS Replication. WMI-based management access occurs over a firewall-friendly Windows Remote Management (WinRM) transport protocol. The previous WMIv1 namespace is still available for backwards compatibility.

  • Cross-file RDC disable, which provides the option to disable cross-file RDC between servers. With this feature, you can choose whether or not to use the cross-file RDC capability, depending on your data and network topologies. For servers on LANs, turning off cross-file RDC may reduce server resource overhead and increase replication performance.

  • File staging tuning, which provides the option to configure variable file staging sizes on individual servers. You can now choose a minimum file size for a file to stage, as long you have not configured RDC for a smaller size. For servers on LANs with larger files, increasing the minimum staging size for files can increase replication performance.

  • Preserved file restoration, which provides the capability to restore files from the ConflictAndDeleted and PreExisting folders. This enables the recovery of obfuscated user data from hidden DFS Replication private folders. You can restore these files and folders into their previous location or a new location, can choose to move or copy the files, and can keep all versions of a file or only the latest version.

Improvements to existing DFS-R functionality include:

  • Unexpected shutdown database recovery, which enables automatic recovery after a loss of power or an unexpected stopping of the DFS Replication service. When DFS Replication detects an unexpected (dirty) database shutdown, such as after a power outage or service termination, it automatically validates the database against the file system and then resumes replication normally, with no files arbitrarily losing conflicts.

  • Membership disabling, which stops DFS Replication private folder cleanup when disabling a server’s membership in a replicated folder. Files that had previously moved to the ConflictAndDeleted or PreExisting folders are no longer deleted when you disable a server’s replication group membership. The message displayed by management tools now states what processing occurs after disabling memberships and explains that re-enabling a membership starts non-authoritative synchronization.

Here are some additional sources of information on the improvements to DFS Replication in Windows Server 2012 R2:

Replication is one of the most sought after functionalities in all of computer science. Being able to seamlessly move, synchronize and make data available in different locations around the globe was considered magic just a few decades ago; now you can do it with ease for a fraction of the cost. When you layer DFS-R on top of award-winning file protocols, file systems, and deduplication capabilities, you can see that you get a lot for your money with Windows Storage Server 2012 R2.

Scott M. Johnson
Senior Program Manager
Windows Storage Server