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:nginx/1.10.1PHP 7.0.8-1~dotdeb+8.1Percona mysql server 5.6.30-76.3-log dovecot 2.2.develpostfix 2.11.3-1java 1.7.0_101We have tried to return to php5.6, disable cron, disable postfix and dovecot, stop our Java app, but nothing helped.The peaks look like the following:The iotop looks like the following:How can I know exactly what causes these peaks and eliminate them?
Disk I/O and load average peaks once every hour
debian;php;disk usage;nginx;load average
The problem was https://developers.google.com/speed/pagespeed/module/ which have done cache clean every hour.Configuration it to store files on tmpfs fixed the problem.