We have updated our server from Debian Wheezy to Jessie and from php5.6 to php7.0, but now we have a disk I/O and load average peak exactly every hour. The exact time depends on the system start time.
On this server, we have:
- PHP 7.0.8-1~dotdeb+8.1
- Percona mysql server 5.6.30-76.3-log
- dovecot 2.2.devel
- postfix 2.11.3-1
- java 1.7.0_101
We have tried to return to php5.6, disable cron, disable postfix and dovecot, stop our Java app, but nothing helped.
How can I know exactly what causes these peaks and eliminate them?