In MySQL a big portion of the problems you’re facing is different
replication delays so there’s no surprise this
is one of the most common interview questions on
DBA interviews and I still found people having
problems with explaining what they would do in a certain
situation. This is why I decided to write a bit about the
99% of times the reason is IO. The slave cannot keep up with the
amount of writes it gets from the binary logs while in parallel
it has to return results of queries as well. In spite of the
common belief in MySQL it’s much easier to saturate the disk
subsystem (even a raid 10 with 8 SAS disk and cache) than the
In this situation all you can do is try to remove some pressure
from the slaves.
One way to do this is setting innodb_flush_log_at_trx_commit
to 2 if it used to be 1. Usually this is enough.