What The Hell Is WS2012 ReFS?

You’ve probably heard of Windows Server 2012 ReFS on podcasts, read about it in articles, and wondered: what the hell is ReFS!?!?

NTFS is ancient by IT terms, dating back to the days when NT was originally written in the early 1990s.  You might remember back in the build up to “Longhorn” (Vista/Server 2008) the talk of a new file system based on SQL Server.  I shat myself every time I thought of it; what a dreadful idea … a file system that would require maybe 16 GB of RAM!

Windows Server 2012 does contain a next generation file system called Resilient File System.  ReFS (pronounced re – fuss) is next generation … at least to me … because CSV doesn’t support it … yet.  I guess that’ll come in vNext (here we are in RTM Week and I’m talking vNext!).

Microsoft posted a document called Application Compatibility and API Support for SMB 3.0, CSVFS, and ReFS.  The following are extracts from this document:


Resilient File System (ReFS) is a new local file system introduced in Windows Server “8”, immediately addressing critical server customer needs, and providing the foundation for future platform evolution, for all Windows customers.


  • Integrity: ReFS stores data in a way that it is protected from many of the common errors that can cause data loss. File system metadata is always protected. Optionally, user data can be protected on a per-volume, per-directory, or per-file basis. If corruption occurs, ReFS can detect and, when configured with Storage Spaces, automatically correct the corruption.
  • Availability: ReFS is designed to prioritize the availability of data. With ReFS, if corruption occurs, and it cannot be repaired automatically, the online salvage process is localized to the area of corruption, requiring no volume down-time.
  • Scalability: ReFS is designed for data sets sizes of today and the data set sizes of tomorrow, optimized for high scalability.
  • Application Compatibility: ReFS supports a subset of NTFS features and Win32 APIs that are widely adopted.
  • Proactive Error Identification: A data integrity scanner (commonly known as a “scrubber”) periodically scans the volume, attempting to identify latent corruption and then proactively triggers a repair of that corrupt data.
  • Architectural Evolution: A new architecture allows ReFS to evolve in conjunction with new storage devices, new data types, and new access patterns, providing a file system platform for the future.

Some Other Notes I Made

  • The document is intended for developers so it goes on to talk lots about APIs and stuff. 
  • ReFS is only in Windows Server 2012 and not in Windows 8.
  • ReFS can be configured only as a data volume; you cannot install an operating system on a ReFS volume or use it as a boot volume.
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