# wsrep\_slave\_threads - how high is high ?

**URL:** <https://forums.percona.com/t/wsrep-slave-threads-how-high-is-high/3231>\
**Category:** Percona XtraDB Cluster 5.x\
**Created:** [January 29, 2014, 8:18am UTC](https://forums.percona.com/t/wsrep-slave-threads-how-high-is-high/3231 "2014-01-29T08:18:28Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dannyg](https://avatars.discourse-cdn.com/v4/letter/d/9fc29f/32.png) [@dannyg](https://forums.percona.com/u/dannyg)\
**Post date:** [January 29, 2014, 8:18am UTC](https://forums.percona.com/t/wsrep-slave-threads-how-high-is-high/3231/1 "2014-01-29T08:18:28Z")

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Hi,

I’ve got a 3 node cluster running on Amazon i2.2xlarge instances (SSD Drives + 60GB Ram + 8 E5-2670 v2 CPU’s).

its working very nice the only problem is that I’m getting a lot of flow controls per day from each node mainly due to our application which does a lot of small writes almost simultaneously.

I’ve been playing around with the amount of slave threads used for parallel replication and i’ve been wondering whats considered a high/good value ? i’ve started with 8 then bounced to 32 and now I’m up to 100 for test purposes, so far the flow-controls seems to have stopped, is this normal ? can i maybe go even higher ? the cpu usage on the nodes is almost idle…

i’ve read somewhere that a good indication is wsrep\_cert\_deps\_distance but this value is always showing 1.000000 on all nodes.

Thanks,  
Danny.

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**Author:** ![przemek](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/przemek/32/3_2.png) [@przemek](https://forums.percona.com/u/przemek)\
**Post date:** [February 1, 2014, 7:15pm UTC](https://forums.percona.com/t/wsrep-slave-threads-how-high-is-high/3231/2 "2014-02-01T19:15:56Z")

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I’d say there is no golden rule, all depends on workload characteristics, hardware, etc. But I think there is no point in setting more then recommended here: [url][http://www.codership.com/wiki/doku.php?id=configuration\_tips#parallel\_applying\_wsrep\_slave\_threads[/url]](http://www.codership.com/wiki/doku.php?id=configuration_tips#parallel_applying_wsrep_slave_threads%5B/url%5D)