It would help in a use-case when there are 2 NGINX processes, both working with the same cache directory.

NGINX-A runs with a proxy-cache-path /disk1/cache with zone name "cacheA".

NGINX-B runs with the same proxy-cache-path /disk1/cache with zone name "cacheB".

When NGINX-B adds content to the cache (say for URL test/a.html), the file gets added to cache as /disk/cache1/test/a.html (again, avoiding md5 for simplicity).

I think it may be nice if a subsequent request for this URL to NGINX-A would result in a hit, as the file is available in the disk. However, today it does not result in a HIT, as the in-memory metadata is missing for NGINX-A for this URL. So, it would fetch from origin and add it again to cache, and update its in-memory metadata.

Otherwise, a restart of NGINX-A would build up the cache metadata for files found in the cache directory.

Thanks
Rajesh