Microsoft is testing an option to install Windows 11 on ReFS instead of NTFS, but surprisingly, it has also confirmed that Windows will block ReFS-formatted USB drives by default starting January 2027.
The October 2026 update already warns users about these drives with Event ID ry, Windows will block them from mounting unless an administrator overrides the restriction.
Your files won't be deleted, but you could lose access to your ReFS USB drive after an update.
Microsoft says ReFS on removable media has never been a supported configuration and cites security as one of the reasons.
In Microsoft's own benchmark, copying a 10GB file took 7.964 seconds on NTFS, compared to just 641 milliseconds on a ReFS Dev Drive with block cloning enabled. That's a massive 92% reduction under those conditions!
I understand why Microsoft might want to restrict unsupported storage configurations, but I wasn't expecting it to block ReFS on USB drives when we've been hoping for ReFS to eventually replace NTFS.
Microsoft hasn't confirmed whether ReFS will become the default file system for Windows 11, and perhaps it'll remain limited to specific workloads.
The October 2026 update already warns users about these drives with Event ID ry, Windows will block them from mounting unless an administrator overrides the restriction.
Your files won't be deleted, but you could lose access to your ReFS USB drive after an update.
Microsoft says ReFS on removable media has never been a supported configuration and cites security as one of the reasons.
In Microsoft's own benchmark, copying a 10GB file took 7.964 seconds on NTFS, compared to just 641 milliseconds on a ReFS Dev Drive with block cloning enabled. That's a massive 92% reduction under those conditions!
I understand why Microsoft might want to restrict unsupported storage configurations, but I wasn't expecting it to block ReFS on USB drives when we've been hoping for ReFS to eventually replace NTFS.
Microsoft hasn't confirmed whether ReFS will become the default file system for Windows 11, and perhaps it'll remain limited to specific workloads.
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More details in our story: windowslatest.com/2026/10/18/win…
Oct 20, 2026 · 6:12 AM UTC
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@WindowsLatest ReFS doesn't have permissions like NTFS last I saw, so might affect things like bitlocker and other permission issues
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