Why swapping is not a good idea in zookeeper and kafka? -

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i have read instructions on

do not use swap

both on zookeeper , kafka. know kafka depends on pagecaching keep parts of sequential logs cached in-memory written disk.

but can not understand how swapping can harm zk , kafka.

swapping may cause performance stability problems; in example, don't want linux kernel "mistakenly/accidentally" swap kafka or zookeeper processes.

also, swapping may particularly bad jvm processes such kafka , zookeeper, quoting:

[the] jvm won't full gc cycle until has run out of allowed heap, of heap occupied not-yet-collected garbage. since these pages aren't being touched (because garbage , unreferenced), os happily swaps them out. when gc runs, have ridiculous swap storm, pulling in these pages discover in fact filled garbage , should discarded; can make gc cycle take many minutes!

hence recommendation disable swapping setting vm.swappiness 0, though operating systems rhel 6.5 should 1 (because semantics of value 0 changed on these os's). note swapping may still occur.

the following links may shed further light on question. explain why disable swapping hadoop , elasticsearch, respectively, , it's same reasons should disable swapping kafka , zookeeper:


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