On 20/02/07, Tzahi Fadida <[EMAIL PROTECTED]> wrote:
On Tuesday 20 February 2007 14:37, Maxim Veksler wrote: > What about redundancy. I need an active-active cluster for databases > to get the 5*'9's up time euphoria. Is there an open source database > that can do that? Planing to? Tried to? PostgreSQL can do that and i am betting MySQL can too. Though not alone. You need an additional product that works with them.
Are you sure you need multi-master (aka active-active) in order to achieve 5 9's? From what I gather multi-master is important for scalability (in terms of "being able to serve a large number of writing clients"). master-slave replication with auto fail-over sounds almost trivial both with MySQL and PostgresQL. According to http://www.postgresql.org/docs/8.2/interactive/failover.htmlthere are commercial solutions to do multi-master that but I couldn't find a pointer to a specific one. There is PGcluster which is supposed to be an open-source solution for multi-master and load balancing, and maybe some sites use it, but it feels a bit like a hack (it's sort of an "SQL reverse proxy" and/or "software mirror RAID", sitting between the clients and the multiple masters, synchronizing changes among the multiple servers), but that's just a feel from reading about it. Check out Slony-l and friends. Usually we are talking about Master-Slave
replication service but i think both can be active. I.e. one point of change,
As far as I read about Slony-I so far - it's the recommended way to do master-slave replication but for master-master support you'll have to wait for Slony-II ( http://www.slony2.org/) which seems to be years away and I'm not sure how active is its development at all (its main Wiki page was last touched almost a year ago). According to the thread on http://gborg.postgresql.org/pipermail/pgreplication-general/2006-May/thread.html#1433 it sounds not so good - some talk about the initial approach found to be unscalable and generally it starts to look like a frozen project. --Amos
