You need to distinguish between memory used for heap and memory used by the operating system cache. Memory is there to be used, and the operating system manages the cache and will evict from it to free up memory as needed, so high cache usage is generally not a problem. This cache is very important to get the best out of Elasticsearch, especially in later versions that use doc_values more extensively, so heap should be set to 50% of RAM to leave a large enough cache.
I already did, even fact lower by 50% by just allocating 12GB to my ES JVM Heap...
So does it mean that even though physical memory RAM usage is 99%, with buff/cache taken most of it, it won't affect ES performance, I shouldn't worry about it?
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