MySQL Cluster: Difference between revisions

Revision as of 15:34, 8 May 2005

Revision as of 14:36, 9 June 2005

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MySQL Cluster has a few important concepts behind its design, which give both benefits and disadvantages.

===Replication===

NDB uses synchronous replication through a two-phase commit mechanism in order to guarenteeguarantee that data is written to multiple nodes upon commitingcommitting the data. Normally there is two copies of the data in the cluster, however it can be configured to allow 1-4 copies at any single time.

===Horizontal Data Partitioning===

Data within NDB tables are automatically partitioned across all of the data nodes in the system. This is done based on a hashing algorithm based on the PRIMARY KEY on the table. This is totally transparent to the end application.

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The largest limitation currently is with the fact that it is an in-memory database. This means that across the cluster setup, you need enough RAM to store the entire dataset.

Another limitation is with how many nodes can be part of the cluster. Currently you can only have up to 64 nodes in the cluster with up to 48 of those being data nodes that store the actual data. It is possible to change this at compile time, but that has not been throughlythoroughly tested at this point.

Also of note, The current maximum number of metadata objects is limited to 1,600. (including database tables, system tables, indexes, etc.)