On 2013-11-15 07:32, Pavel Ivanov wrote:
Semi-sync replication for us is a DBA tool that helps to achieve durability of transactions in the world where MySQL doesn't do any flushes to disk. As you may guess by removing disk flushes we can achieve a very high transaction throughput. Plus if we accept the reality that disks can fail and repairing information from it is time-consuming and expensive (if at all possible), with such reality you can realize that flush or no flush there's no durability if disk fails, and thus disk flushes don't make much sense. So to get durability we use semi-sync. And definition of "durability" in this case is "if client gets ok on the transaction he will find this data after that". And that should stand in case of any master failures and failovers.
Hi Pavel, Please pardon this arrogant interruption of your discussion and shameless self-promotion, but I just could not help noticing that Galera replication was designed specifically with these goals in mind. And it does seem to achieve them better than semi-sync plugin. Have you considered Galera? What makes you prefer semi-sync over Galera, if I may ask? Kind regards, Alex
Pavel
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