Comments - PORTING MYSQL V5.5.19 TO MARIADB MASTER-MASTER SETUP
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Hi Christine
If you are happy with what you get today, you can upgrade and get the same architecture with better performance for replication.
Your current architecture is eventually consistent and can be made more robust in ROW BASED an mode IDEMPOTENT. see https://mariadb.org/mariadb-eventually-consistent/
Galera will instead assume that all data writes should at least reach a majority of node before commit, so it's more sensible to network communication or big write transactions but can really simplified automation of application failover, because a write is visible when it's already propagated.
If you wan't to provide Availability of storage when a node found itself isolated from network. Galera is not the correct solution and you will have to stay with asynchronous replication and paying the price of eventually consistency when the diverging dataset are merged. To limit such issues one can use semi-sync to limit dataset divergence, delaying commit until data reach an other node but below a given timeout. Using 10.1 is a must do for semi-sync because it improved performance of such replication mode.
You can draw multi-master replication as a versioning application like Github , when you get merging code issues, a manual conflict resolution is multi master. Automatic conflict resolution telling last commit win, is idempotent mode. Now Galera is a efficient way to prevent you to change same code just when you are modifying it.
Many players decided not to enable diverging datasets , so they use active /passive solutions and an improved architecture call Master Election .
/Svar
Thank you for getting back to me so quickly. Your responses are very informational.
I wanted to make sure that our current setup, where both master servers can receive database updates, is still available without Galera. I will review the suggestions with the senior mysql engineers.
Again, thank you.