Noticed that MySQL replication is generating enormous disk write activity
AWS volume monitor - 700-800 IOPS (while only 150 IOPS on master)
And it lasts for hours. Historical graphs show that this repeats every day for 8-10 hours. (I think until the moment when catch up is finished)
Replication processes in the state: “Reading event from the relay log” and “Waiting for master to send event”
Replication is lagging behind master, it is running but VERY slow.
There are no active processes in MySQL that can generate this activity. No backups at this time. Replication activity is constant but not so high to generate this problem.
If I stop slave SQL thread - activity drops to zero immediately. After starting slave it increases again. Restarting mysqld doesn’t help.
What parameters/configs/metrics sould I check?
Any help would be appreciated.
Percona server 5.5 on CentOS
Replicated database about 500Gb, about 300 tables.