Kind of..lets see if I got this..so with my first setup, which was just 1 controller, that controller talks to both my db backends (i.e. I had 2 backends in the virtual database config file), but now with the setup of an additional controller, I should move the backend config for the 2nd database server to the 2nd controller? So each controller is only talking to 1 backend? If so, what happens when I add a 3rd database server/backend? In what controller would that get configured? If I add it to just one controller, and that controller goes down, then I lose consistency on that backend through the 2nd controller (which doesn't have it configured), if it was configured on both I'd have multiple writes and inconcsistency again, as you mentioned. Would I need a third controller then?
Thanx, -Tony --------------------------- Manager, IT Operations Format Dynamics, Inc. 303-573-1800x27 [EMAIL PROTECTED] http://www.formatdynamics.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, June 11, 2008 11:42 AM To: Sequoia general mailing list Subject: Re: [Sequoia] help understanding multiple controllers with disk space usage 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 _______________________________________________ Sequoia mailing list [email protected] https://forge.continuent.org/mailman/listinfo/sequoia
