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Ahoi Pavel, On Fri, Nov 15, 2013 at 01:59:49PM -0800, Pavel Ivanov wrote: [snip]
As an example here's an independent comparison of Galera vs. semi-sync performance: http://linsenraum.de/erkules/2011/06/momentum-galera.html.
This is a nice blog post written in German and posted in 2011. And while Google Translate gave me an idea what post was about it would be nice to see something more recent and with better description of what was the actual testing set up.
it is my post and as a fact you are right a newer one would be also nice. As a fact there is one: http://linsenraum.de/erkules/2012/03/galera-als-replikationsersatz.html (Even there is a mistake: missing setting for innodb_flush_log_at_trx_commit=0). There you also get some infos about the used hardware I think Im going to write a new one. Also with newer hardware. And there will be an English version. The basic idea oft the tests is. Not to rely on the 'master'. Thats why I used settings like innodb_flush_log_at_trx_commit=0 and innodb_doublewrite=0 The basic idea is not to rely on any data of a crushed node. Working also in 'cloudenvironments' I prefer to rebuild instead to repair a node. To make it short. * Galera is always faster than Semisync. You can compare it to async repl. It gets his speed out of the parallel applying. * With Galera you have (virtual) synchronous replication. Using Semisync you know nothing. All you can do is monitoring semisync variables. But I doubt it will tell you anything about the 'last' transactions So you got async repl speed with synchronous data \o/ Regards Erkan -- über den grenzen muß die freiheit wohl wolkenlos sein