we are implementing ES in Magento 2.2.2 and we are facing an infrastructure issue.
What we are seeing is that ES 5.6.8 uses more memory than ES 2.4.6 (a huge more than 2.4.6). Basically 5.6.8 takes 2.5gb RAM just from the start and with 2.4.6 it was around 700 mb or something similar.
In DEV environments we have ES in the same server than Magento, so when we enable the cronjobs the memory goes to top, and the server falls appart.
Does anybody have the same issue? Does anybody know why ES 5.x requires that huge amount of RAM?