Insight for DBAs

Jeremy Cole on MySQL Replication

Jeremy Cole recently posted very nice post about MySQL Replication Performance. There are however few points I should comment on.

Jeremy Speaks about MyISAM and Innodb in the same terms, in fact they are quite different for Replication. As you probably know MyISAM uses buffered IO so if master crashes you’re out of sync […]

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Group commit and XA

Returning to post Group commit and real fsync I made several experiments:
I ran sysbench update_key benchmarks without —log-bin, with —log-bin, and with —log-bin and —innodb-support-xa=0 (default value is 1). Results (in transactions / sec)

threads
without —log-bin
—log-bin
—log-bin and
—innodb_support-xa=0

1
1218.68
614.94
1010.44

4
2686.36
667.77
1162.60

16
3993.59
666.14
1161.56

64
3630.55
665.18
1151.36

So we can see group commit is not only broken when XA is enabled but also if XA […]

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MySQL Server Memory Usage

Every so often people ask me the question how should they estimate memory consumption by MySQL Server in given configuration. What is the formula they could use.
The reasons to worry about memory usage are quite understandable. If you configure MySQL Server so it uses too small amount of memory it will likey perform suboptimally. […]

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