I found around 6-15% performance improvement in build times after implementing DevDrive (mounted VHD) on Windows machines, which uses ReFS. Deleting huge folders was also perceivably faster.

I have been made aware of ReFS thanks to the "Dev drive"[1] technology in Win11. ReFS is apparently particularly suited to store source code and code artifacts for dev workloads.

I have been using it (dedicated DevDrive partition) for some time but performance improvement are subtle and not easily visible without measurements. Which I haven't done.

[1] https://learn.microsoft.com/en-us/windows/dev-drive/

IIRC, because I am old, NT 3.1/3.51 supported HPFS from OS/2. Now get off my lawn.

> Microsoft is testing

This is a contradiction in terms. Microsoft doesn't test anything. Always the user has to do it.