Optimal DB configuration (MySQL)

[authex]

Hi there,
I was wondering if anyone could lend any help; I'm running the following setup:

Ubuntu 14.04.2 LTS
Zabbix Server Version 2.2.9
MySQL Version 14.14

My environment was running perfectly fine; but then we got spikes on "Zabbix unreachable poller processes more than 75% busy"

Ever since then, we are unable to get information about 3 servers (Ping) graphs; therefore, showing offline in Zabbix.

As far as the number of hosts; we only have 25 clients, running approx 70 values per second.

Please review my.cnf below:

[client]
port            = 3306
socket          = /var/run/mysqld/mysqld.sock

[mysqld_safe]
socket          = /var/run/mysqld/mysqld.sock
nice            = 0

[mysqld]
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
lc-messages-dir = /usr/share/mysql
skip-external-locking

bind-address            = 127.0.0.1

key_buffer              = 16M
max_allowed_packet      = 16M
thread_stack            = 192K
thread_cache_size       = 8

myisam-recover         = BACKUP
max_connections        = 500

query_cache_limit       = 100M
query_cache_size        = 100M

log_error = /var/log/mysql/error.log

expire_logs_days        = 10
max_binlog_size         = 100M

[mysqldump]
quick
quote-names
max_allowed_packet      = 16M

[mysql]
#no-auto-rehash 

[isamchk]
key_buffer              = 16M

!includedir /etc/mysql/conf.d/

[kloczek]

My environment was running perfectly fine; but then we got spikes on "Zabbix unreachable poller processes more than 75% busy"

Because probably you are still using passive items (not "Zabbix agent (active)" type).

I've not been using MyISAM very long time and IIRC this engine does not support foreign keys which are used by zabbix schema.
If I'm right and if you been doing some delete operations on hosts or templates you may hove already some garbage on DB.

$ grep -c "FOREIGN KEY" schema.sql 
134

Most of FKs are on delete cascade.