With use of proxy_cache_min_uses volume of cache is getting settled up at around 50% utilization.
No matter what is the volume allocated in max_size its not filling up further beyond 50%.
If the proxy_cache_min_uses is removed the cache gets filled up with max_size allocated volume.

No of files in cache directory is far less beyond the size allocated in key zone. Its getting capped up near 20 Lakhs whereas allocated key zone could have accommodate around 80 L files with below configuration

proxy_cache_path /cache/contentcache keys_zone=content:1000m levels=1:2 max_size=1000g inactive=7d use_temp_path=off;

proxy_cache_min_uses 2;

Cache volume is utilized with above configuration is around 550 GB which is not growing beyond and as inactive is set to 7d so this would have been effective only after 7 days when content should have got deleted if not accessed within 7 days time period.

Writing all the objects on disk is causing high i/o so using proxy_cache_min_uses would have been beneficial with utilizing cache optimally and high cache hit ratio