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sorano de19cfa38b Update Performance.md

Clarified that the mysqld performance options need to be put under a [mysqld] group in my.cnf. Since in Ubuntu 16.04 /etc/mysql/my.cnf only has [client-server] group by default which is not a valid group for the changes we make.

2016-09-23 08:22:47 +02:00

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source: Support/Performance.md

Performance optimisations

This document will give you some guidance on optimising your setup.

The suggestions are in a rough order of how much impact they will have.

RRDCached

We absolutely recommend running this, it will save on IO load. RRDCached

MySQL Optimisation

It's advisable after 24 hours of running MySQL that you run (MySQL Tuner)[https://raw.githubusercontent.com/major/MySQLTuner-perl/master/mysqltuner.pl] which will make suggestions on things you can change specific to your setup.

One recommendation we can make is that you set the following in my.cnf under a [mysqld] group:

innodb_flush_log_at_trx_commit = 0

You can also set this to 2. This will have the possibility that you could lose up to 1 second on mysql data in the event MySQL crashes or your server does but it provides an amazing difference in IO use.

Polling modules

Disable polling (and discovery) modules that you do not need. You can do this globally in config.php like:

Disable OSPF polling

$config['poller_modules']['ospf'] = 0;

You can disable modules globally then re-enable the module per device or the opposite way. For a list of modules please see Poller modules

SNMP Max Repeaters

We have support for SNMP Max repeaters which can be handy on devices where we poll a lot of ports or bgp sessions for instance and where snmpwalk or snmpbulkwalk is used. This needs to be enabled on a per device basis under edit device -> snmp -> Max repeaters.

It's advisable to test the time taken to snmpwalk IF-MIB or something similar to work out what the best value is. To do this run the following but replace with varying numbers from 10 upto around 50. You will also need to set the correct snmp version, hostname and community string:

time snmpbulkwalk -v2c -cpublic HOSTNAME -Cr<REPEATERS> -M /opt/librenms/mibs -m IF-MIB

NOTE: Do not go blindly setting this value as you can impact polling negatively.

Optimise poller-wrapper

The default 16 threads that poller-wrapper.py runs as isn't necessarily the optimal number. A general rule of thumb is 2 threads per core but we suggest that you play around with lowering / increasing the number until you get the optimal value.

Recursive DNS

If your install uses hostnames for devices and you have quite a lot then it's advisable to setup a local recursive dns instance on the LibreNMS server. Something like pdns-recursor can be used and then configure /etc/resolv.conf to use 127.0.0.1 for queries.

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