On Thu, 2008-05-29 at 23:37 +0200, Mathias Brossard wrote: > I pointed out that the NTT solution is synchronous because Tom said in > the first part of his email that: > > > In practice, simple asynchronous single-master-multiple-slave > > replication covers a respectable fraction of use cases, so we have > > concluded that we should allow such a feature to be included in the > > core project. > > ... and yet "the most appropriate base technology for this" is > synchronous and maybe I should have also pointed out in my previous mail > is that it doesn't support multiple slaves.
I don't think that you need too many slaves in sync mode. Probably 1-st slave sync and others async from there on will be good enough. > Also, as other have pointed out there are different interpretations of > "synchronous" depending on wether the WAL data has reached the other end > of the network connection, a safe disk checkpoint or the slave DB itself. Probably all DRBD-s levels ( A) data sent to network, B) data received, C) data written to disk) should be supported + C1) data replayed in slave DB. C1 meaning that it can be done in parallel with C) Then each DBA can set it up depending on what he trusts - network, slave's power supply or slaves' disk. Also, the case of slave failure should be addressed. I don't think that the best solution is halting all ops on master if slave/network fails. Maybe we should allow also a setup with 2-3 slaves, where operations can continue when at least 1 slave is "syncing" ? -------------- Hannu -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
