[German]The ReFS file system introduced by Microsoft in Windows a long time ago seems to be a "stepchild" of the developers. Bugs are never fixed – even with Windows Server 2025, the May 2025 patchday has not changed the problem that ReFS-formed disks lead to high CPU/RAM utilization, making the server unusable.
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The Resilient File System (ReFS)
ReFS was introduced by Microsoft as a "new" file system with the Windows 8 and Windows Server 2012 operating systems (see my German blog post Windows 8 Storage Space und ReFS). In addition to compatibility with the NTFS file system, Microsoft promised many advantages such as a transaction model for maintaining consistency, including checking data when reading and writing, error tolerance through redundancy, auto-correction when data errors are detected, etc. Microsoft has published the article Resilient File System (ReFS) overview with some explanations.
Somehow an unbeloved stepchild
In view of the advantages outlined above and its introduction over a decade ago, ReFS should actually be the "philosopher's stone" for Microsoft. To me, however, ReFS seems more like a stepchild that is hidden away and not particularly cared for.
With the Fall Creators Update (version 1709), the creation of new partitions with ReFS was partially canceled for Windows 10 (see Windows 10 Version 1709: ReFS will be removed (partially)). Such data carriers can now only be created in the Enterprise and Pro for Workstations versions.
In addition, administrators who format disks with the ReFS file system repeatedly run into bugs that are not fixed for a long time. I remind you of my blog posts Out-of-Band Updates for Windows (Jan. 17/18, 2022) doesn't fixes ReFS Issues complete andMicrosoft and the unfixed ReFS bug in Windows. Microsoft is just an "innovative company" that wants to be ahead in AI, so such lowlights are of no interest.
Windows Server 2025 and the ReFS bug
There is a nasty bug in the ReFS file system in Windows Server 2025, Microsoft's flagship server product. Blog reader Daniel A. noted in this German commentt: "Too bad, the ReFS problem under Server 2025 is apparently not being addressed". The bug was not fixed with the May 2025 updates either.
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Regarding the ReFS bug, Daniel wrote in another German comment that under Windows Server 2025, in conjunction with ReFS-formatted drives, there is a massive utilization of CPU/RAM. This probably goes so far that the server becomes unusable after a short time, it depends on how much CPU/RAM is installed.
According to readers, the bug was confirmed by Microsoft to the backup provider Veeam. In the Veeam forum there is a discussion in the thread Server 2025 – high CPU and RAM – and in this thread someone blames it on a cache limit.
The reader states that Microsoft has probably sent the Veeam developers a patch that is not publicly available (presumably for testing). According to Daniel A., however, this fix – at least according to the KB articles – was not rolled out in the cumulative update for Windows Server 2025 on May 13, 2025. If I look at the blog posts linked below, the bug could be dormant in Windows Server 2025 for even longer. Or does anyone have other information?
Similar articles:
Windows 8: Neuigkeiten zum ReFS-Dateisystem
Windows 10 Version 1709: ReFS will be removed (partially)
Out-of-Band Updates for Windows (Jan. 17/18, 2022) doesn't fixes ReFS Issues complete
Microsoft and the unfixed ReFS bug in Windows
Windows 11 24H2/Server 2025 with huge Hyper-V bug?
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