ES heap memory and OS filecaching


Do we have to keep the same amount of memory available for the OS as for Elasticsearch ?

So if I have 16Go memory available on the machine, should I set JMX/JMS to 8Go and keep another 8Go free for the OS in order to allow efficient filecaching ? Or can I set JMX/JMS to something like 14Go ?

Keeping heap at 50% of RAM is recommended as the file system cache is important for performance.

Here are two docs to help you out with heap sizing: the official doc and a really thorough blog post. The second one is a really good read and will explain why you want to allocate about 50/50 between heap and OS. Happy reading!

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