Improvement on the I/O section of the Improving Performance document [JIRA: DOC-774]

[pogzie]

http://docs.basho.com/riak/kv/2.1.4/using/performance/#optional-i-o-settings cites that

vm.dirty_background_ratio = 0
vm.dirty_background_bytes = 209715200
vm.dirty_ratio = 40
vm.dirty_bytes = 0
vm.dirty_writeback_centisecs = 100
vm.dirty_expire_centisecs = 200

It was noticed that setting the values could possibly overwrite the other corresponding config parameter.

dirty_background_bytes is the counterpart of dirty_background_ratio. Only one of them may be specified at a time. When one sysctl is written it is immediately taken into account to evaluate the dirty memory limits and the other appears as 0 when read.

https://www.kernel.org/doc/Documentation/sysctl/vm.txt

Will continue to review and possibly test modifications and file a PR for a correction.

[glickbot]

Good catch with the wording, it is definitely the case that either ratio, or bytes should be set for dirty_ and dirty_background_ settings. Those settings are a starting point for further benchmarking and performance analysis (for 16GB machines), and either the dirty_ratio/dirty_background_ratio or dirty_bytes/dirty_background bytes should be applied depending on how the user wishes to apply them.