Hi Dojo,
I have Linux nodes for Cassandra and ElasticSearch on which the swap memory is disabled. Is it advised to enable swap memory?
Jens Vandewalle [SLC] [DevOps Enabler] Selected answer as best 12th January 2022
Hi Jens,
For both Cassandra and Elastic, it's advised to disable swap memory.
While the system will work with swap enabled, the performance will be very poor when the system starts to use the swap memory.
Some recommendations from elastic can be found here
Some recommendations from datastax on Cassandra can be found here
Srikanth Mandava [SLC] [DevOps Member] Posted new comment 14th January 2022
Ive’s Cassandra link already says this, but just to make this explicit.
“If you insist on using swap, you can set vm.swappiness=1. This allows the kernel swap out the absolute least used parts.”
If the system is expected to run even when it reaches the high memory usage rather than crashing and creating outage to the services , then configuring swappiness is very effective. On Linux, by default this is set to 60 and this can be configured to define when the system can use the swap space from the disk.
https://linuxhint.com/understanding_vm_swappiness/ has more details and explanation.