Hi Dejan
There are a couple of things that are contributing to some confusion here.
The first is that the currently available documentation doesn’t do a great job of explaining that it is possible to enable bypass-IO on a file hosted on a volume where the filter stack supports bypass-IO, but the underlying storage stack does not. In such a scenario (which I suspect is what you’re seeing), reads for bypass-IO enabled files will bypass the filter stack, but still be sent down the volume stack. I will file a documentation bug to better explain this.
The second is that FsUtil wasn’t providing much help in understanding this. This has been addressed with more recent builds of Windows (this is output from one of my machines running Windows 11 22H2):
PS C:> fsutil.exe bypassio state c:
BypassIo on "c:" is partially supported
Volume stack bypass is disabled (iaStorAVC.sys)
Storage Type: RAID
Storage Driver: Not BypassIo Compatible
Dave Buches
Windows CoreFS Dev