In this blog post we provide a high-level overview of the Resilient File System (ReFS), Microsoft’s next-generation file system that is included in Windows Server 2012.

UPDATE: Thanks to the sharp eyes of 4sysops readers Vital and Ben, I’ve updated this post to correct some file system statistics. As you know, a technical article must be 100 percent correct or it becomes essentially worthless.

When I entered the information technology (IT) industry as a junior Windows systems administrator in 1997, New Technology File System (NTFS) was the only reasonable file system choice for Windows Server systems.

Recall that a file system is a mechanism for organizing files on a magnetic or solid-state hard drive. We apply a file system to a volume once we have (a) defined a partition structure; and are (b) ready to format that partition. In Windows, a formatted partition is typically assigned a drive letter for easy reference.

The chief advantages of NTFS are:

  • Support for larger volume sizes (up to 256 TB thanks to GPT)
  • Discretionary Access Control Lists (DACLs)
  • File system journaling to (supposedly) limit the possibility of file corruption
  • Encrypting File System (EFS)
  • Advanced auditing
  • Quotas
  • File compression
  • Volume Shadow Copy

The list goes on. The way I describe NTFS to students is that “NTFS enables us to unlock the complete feature set of Windows Server.”

If NTFS is such as wonderful file system, then why did Microsoft develop the Resilient File System (ReFS) that is available in Windows Server 8 Beta? (Incidentally, I will refer to Windows Server 8 as Windows Server 2012 henceforth due to Microsoft’s formal adoption of that product name.)

It seems to me that Microsoft designed ReFS to grow with trends in storage technology as well as to complement its new Storage Spaces server feature. We’ll discuss more of both of these aspects later on in this review.

NOTE: Because this blog post covers features included in the Windows Server 2012 Release Candidate, this information is subject to change upon the final release of Windows Server 2012.

ReFS features ^

According to Microsoft, the following represent the chief design goals of ReFS:

Backward compatibility. Most (but not all) NTFS features are retained in ReFS. Specifically, the following NTFS features are deprecated in ReFS:

  • 8.3 short file names
  • Compression
  • EFS
  • Hard links
  • Extended attributes
  • Quota
  • Named streams

NOTE: I have verified that Volume Shadow Copies work just fine on ReFS volumes. Therefore, you worried Windows systems administrators who rely upon this feature can heave a sigh of relief!

ReFS read/write performance is believed to be on par with that of NTFS.

Data Verification and Auto-Correction. This is a big selling point of ReFS. NTFS is known as a “self-healing” file system, but if you are like me you have nonetheless experienced partial or full file system corruption. One problem with NTFS is that files are stored as byte streams and file metadata is written and overwritten in-place.

By constrast, ReFS makes metadata updates without disturbing the original metadata. In addition, ReFS includes checksumming and “scrubbing” technology that proactively scans and repairs bad disk clusters. These aspects of ReFS are similar to those of the “cursed” WinFS file system that Microsoft was never quite able to get off the ground.

Scalability. As we mentioned earlier, ReFS was designed in conjunction with Storage Spaces. Storage Spaces is a Windows Server 2012 role service that enables us to create logical storage pools from multiple physical disks. The notion is that we can dynamically shrink and expand our storage pools without perturbing any data contained therein.

Storage Spaces also supports mirroring and striping, and has as its goal to make storage cheaper and more flexible for small businesses. After all, smaller shops tend to have “Just a Bunch of Drives” (JBOD) storage systems as opposed to the hardware RAID arrays embraced by enterprise environments.

Resilient File System (ReFS)- Windows Server 2012 Storage Spaces

Resilient File System (ReFS)- Windows Server 2012 Storage Spaces

ReFS “gotchas” ^

As of the Windows Server 2012 Release Candidate (Build 8400), ReFS cannot be used for boot drives. Microsoft states in their literature that ReFS is optimized for file storage and not process execution. Moreover, we cannot convert an existing NTFS volume to ReFS like we can convert a FAT32 volume to NTFS by using Convert.exe.

We also cannot format removable drives with ReFS. Finally, ReFS is available only in Windows Server 2012. Whether Microsoft will equip Windows 8 with ReFS support remains to be seen.

Interacting with ReFS ^

We can see ReFS in action first of all when we format a volume by using the Windows Server 2012 Disk Management console. The Simple Volume Wizard interface is shown in the following figure.

Resilient File System - Creating a simple ReFS volume

Resilient File System - Creating a simple ReFS volume

The second area where ReFS comes into play is the previously mentioned Storage Spaces role service.

Resilient File System -Creating an ReFS-based storage pool

Resilient File System -Creating an ReFS-based storage pool

Conclusion ^

If you check out the related Internet resources I provide for you below, you will observe fiery arguments among the Windows systems administrator community with regard to ReFS. Some people claim that ReFS is a necessary upgrade to NTFS. Other folks claim that Microsoft is ripping off parts of the Sun/Oracle ZFS file system. Yet other folks decry that Microsoft should have leveraged parts of the ext4 or Btrfs file systems.

All those points are academic. The bottom line is that as Windows systems administrators we need to familiarize ourselves with the objective pros and cons of ReFS because this file system isn’t going away anytime soon. Please feel free to share your observations in the comments portion of this post.

Related Resources:

10 Comments
  1. ben 9 years ago

    what about Volume Shadow Copy?
    I also think the 64 limit should be increase to at least 512 if not 1024

  2. Vital Koshalew 9 years ago

    Windows 2000 era TechNet article is not the best source of information when writing about modern technologies.
    With GPT partitioning you can have raw partition of 18 Exabytes therefore maximum NTFS volume size is 16TB for traditional 4kB cluster size and 256TB for 64kB cluster.

  3. Tim Warner 9 years ago

    Hi Ben and Vital,

    Thanks for the request for clarification; I appreciate your fedback very much. I am revising the article and will credit you both when Michael posts the update. Kindest regards, Tim

  4. Alex Jorge 9 years ago

    This is one of the most professional Page about this subject.
    I want to congratulate the writer.

    I personally just need (I know I'm a foreigner and little slow in my Broken-English LOL ) Better location of [Simple Volume Wizard]in Windows Server 2012 or any software to do it... I just right click in my Windows 8 x64 8400 [LITE] and gives me the option to format my backup partition in ReFS (but I don't do it) I just want to know any software capable to do it out side Windows OS's.

    Thanks and again Congrat's

    Alex Jorge

  5. Alex Jorge 9 years ago

    By the way I just found a very very very Interest View point About ReFS Bad Indicators in this page:

    http://arstechnica.com/civis/viewtopic.php?f=14&t=1165480

  6. Tim Warner 9 years ago

    Thanks for the compliment and the supplemental link, Alex. I appreciate your feedback very much. Take care, Tim

  7. Markus Roedel 9 years ago

    One more 'gotcha' of ReFS is that deduplication is not supported - a major loss of new functionalities that Winsrv 2012 offers...

    Best,
    Markus

  8. ERT 9 years ago

    Are you sure about Bitlocker being not supported in ReFS? A quick google search shows contradictory answers. This MSDN blog states that it is supported:
    http://blogs.msdn.com/b/b8/archive/2012/01/16/building-the-next-generation-file-system-for-windows-refs.aspx

  9. Tim Warner 9 years ago

    Hi ERT. Thanks for bringing up the question--you're correct. I will ask Michael to edit my blog post to reflect the change. -Tim

  10. Matt K 8 years ago

    I know this article is a bit old, but another gotcha of ReFS (at least as of June 2013) is that if you do manage to fill up a drive using ReFS, that drive is toast. This bit me on a production Hyper-V iSCSI host that I wound up having to recover from backup. Not cool for a "resilient" file system.

    To be more clear. There is some mechanism in ReFS that goes nuts when the drive has no more room. When attempting to access a full drive, you receive a "Drive:\ is not accessible. The volume repair was not successful"

    See here:
    http://social.technet.microsoft.com/Forums/en-US/winserver8gen/thread/7abf7f65-1f0f-4766-8894-ae56b85b3700/

    and here:
    http://social.technet.microsoft.com/Forums/en-US/winserver8gen/thread/171a1808-157e-4ef9-b0dd-8a507ff6fcef/

    ReFS has some neat features but it is definitely not ready for production machines just yet.

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