We recently reinstalled 3 of our mysql servers running in master slave with percona 5.7 and ubuntu 18.04 instead of oracle linux 7. These servers are currently connected to a mysql 5.6 master. And since the reinstallation we are getting way more slave lag than when we were running mysql 5.6 on the slaves (it was almost non existent).
The 5.7 servers have the same hardware just some more disks. And instead of one span of 12 disks the reinstalled servers are using 2 spans of 10disks. Both are running on an lvm.
All servers 5.6 and 5.7 are running the noop scheduler and we tested the server raid performance before installing using fio which was all fine (200k random iops). We tried to fine tune the 5.7 settings to mimic the 5.6 master as much as possible.
set global optimizer_switch='derived_merge=off,duplicateweedout=off,condition_fanout_filter=off';We run a fairly big database 3TB on dual cpu xeon’s with 512GB ram optimizing our schema is in progress but far from finished.
It looks like the slaves are lagging on the sql_thread and not the io thread.
Do you guys have any idea why the performance of 5.7 is worse then 5.6?
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Source : Link , Question Author : Jan Willem Mannaerts , Answer Author : Community
