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Both MySQL Cluster and MultiMaster replication give you constant access to your data on more nodes . For lots of shops, those not needing to scale, those that can live with a limited downtime, DRBD and MySQL is a good match, But if you want to achieve real high availability as compared to less downtime. or if you are looking to scale your MySQL and want to benefit from HA while you are at it , then MultiMaster is probably the preferred alternative as opposed to DRBD

The side question about it is of course the fact you have to be picky about storage engines you’re using - DRBD does not work with MyISAM (check required) so you need to have processes to ensure your application does not uses this storage engine which may be hard to guaranty in many environments when development has too much autonomy

The state of High Availability Solutions for MySQL these days is - you can’t have it all. There is no OpenSource solution out where which would offer you full redundancy use of both nodes at least for reads no transaction loss and automated fail over. Whenever you’re using MySQL Cluster, DRBD or MySQL Replication you have to have some compromises.

Protocol C is really the only one that gives any extra data security over binary log replication so it’s the one I’m focusing my attention on. If an issue on one master causes problems on another then the benefit of having redundant masters is effectively lost.

ith DRBD the second master lagging behind because of a degraded raid, network issue, operator error, name your poison causes issues on the primary master because MySQL has to wait for writes to be synced to disk on _both_ machines before continuing

When DRBD, the operating system, or hardware crashes it crashes hard. Any corruption on the primary master during a nasty failure gets happily propagated over DRBD. Binary log replication executes queries on the slave the same way they were executed on the master giving a better chance of a tickled kernel/filesystem bug on one master won’t be ticked on the other master. The primary master will simply crash leaving the secondary master in a consistent state waiting to take on live traffic.