How does ES use RAM? Speccing new server.

[RobParker]

I was hoping someone could give me a quick answer.

Our hosts (Nimbus, who are excellent) are looking to move us to a new server but it'd have less memory.

I'm a little confused on how this would impact ES.

Our live stats show:
KiB Mem : 32652304 total, 5929716 free, 9955640 used, 16766948 buff/cache

I thought a lot of this buffer/cache was ES but our hosts said that ES is using only 6% of the memory (so around 2GB):
PID USER %MEM COMMAND
22671 elastic+ 6.3

In the XF admin page I see:
Documents 7,749,372 (5.6 GB)
Index updates 1,882,146
Searches 4,210,905 (7 milliseconds average)
Allocated memory 7.3 MB

Based on the above, would 24GB of RAM on a new server be sufficient? What memory is ES actually using here?

 

[Xon]

That's odd. Typically, a very small number of keywords account for more than 95% of searches, and once that's cached they should be lightning fast. Even cache misses shouldn't be much slower, in my experience.

I've seen some 3rd party add-ons which push a complex query to elasticsearch on every page load, this can quickly cause performance issues