is cache-only-prefixes an nnpfs limitation?

[Harald Barth]

> > I have an idea, could the 1:1 mapping stay, with the cache file becoming a
> > "sparse file"?  The "holes" would fill the part of the cache file that
> > does not contain valid data.

This would mean that your cache file system or cache memory must support 64-bit
addressing. I would not like that requirement.

> That means cache eviction of parts of files, and making new holes
> in files doesn't seem to be widely supported yet.

Yes. When reading a big file, it must be possible to throw away the
beginning or middle to be able to fit the end in the cache.

Harald.