Slave in replication lags behind the master, if he is far behind
~200 requests per second
If you run the slave with a fresh dump, i.e. when the difference in data is small, it quickly catches up to the wizard and then everything is fine.
If the slave to stop for a couple of days and then again start it somewhere for a minute or two very jauntily begins to catch up (high CPU usage, I / o, all as provisions). And then almost falls asleep — CPU load 1%, a small I / o, and Seconds_Behind_Master is reduced very slowly, standing still or even increased.
Performance iron slave and higher versions of the software are identical. Errors in the logs no. Between servers Gigabit.
it seems understood
the problem in bcache — merged base on a clean SSD and everything flew.
%iowait remained about the same — 5.4
maybe bcache problem with multithreaded access because the synthetics all the chocolate.
in any case, the issue is closed, MySQL is not to blame :)
Brycen answered on October 3rd 19 at 03:47
1. to make sure that replication works. That is, if there are any kind of error SHOW SLAVE STATUS\G in a variable Last_Error
2. To check the age of binari logs on the master. Maybe they 2 days time to leave.