Pure virtual file system (without any kind of caching/hydrating)

[fiddyschmitt]

Is there a way to stop ProjFS from making a physical file when a virtual file is read?

In my backing store, I have a list of virtual files.

public class VirtualFile
{
    public string Filename;
    public Stream Stream;
}

If the contents of a virtual file are requested, I can just read from the Stream to get the requested bytes. The issue is that ProjFS creates a physical file with those contents, which I want to avoid. This is because the Streams I'm dealing with are much larger than the HDD's capacity.

So is there a way to not create physical files, and instead just respond with populated buffers like we can in Dokany?

[cgallred]

No, that isn't currently possible. ProjFS was originally designed to allow us to project an extremely large git repo onto developer workstations. We wanted the performance of the developer's code-build-test cycle to be comparable to what you'd get if the files were locally present, so ProjFS essentially uses the local file system as a cache of the backing store. That lets us amortize the retrieval delay across the time the file is used. Given that scenario focus, we didn't include a streaming mode in it.

[fiddyschmitt]

Understand; thanks for the explanation Christian

[fiddyschmitt]

Hi Christian, Happy New Year!

Is streaming mode on the cards? It would let me use ProjFS for some interesting use cases.

Thanks, Fidel

[cbenhagen]

@cgallred do you have any news on this? We also have a use case where caching locally needs to be disabled.