Hi Tony, >>From reading the docs, backends cannot be shared between controllers, so > does that mean that a 2nd controller added (in a RAIDb1 scenario) > reduces disk space on each database server by half?? E.g. if I have 2 db > servers, each with 500GB of space and one controller (w/2 backends), the > database on each server can grow to 500GB, but with 2 controllers, > there's 2 copies of the database on each server, so it could only go up > to 250GB then? And then if 3 controllers, the space would be 1/3 of > 500GB (166.67GB). > Am I understanding this correctly?
No. The only thing it means is that each db server can only be accessed by a single controller. If you have 1 controller, your 2 db servers must be attached to that controller. If you have 2 controllers, each controller is connected to 1 db server. If you have 3 controllers, 1 controller will have no database server, and the 2 others will have one each. As each controller sends the write queries to all its attached backend, a backend attached to multiple controllers would receive the same query multiple times and be inconsistent. Does that make sense? Emmanuel _______________________________________________ Sequoia mailing list [email protected] https://forge.continuent.org/mailman/listinfo/sequoia
