Re: Core team statement on replication in PostgreSQL

Josh Berkus <josh(at)agliodbs(dot)com> wrote:

> I still see having 2 different settings:
>
> Synchronous: XID visibility is pushed to the master. Maintains synchronous
> failover, and users are expected to run *1* master to *1* slave for most
> installations.
>
> Asynchronous: replication stops on the slave whenever minxid gets out of
> synch. Could have multiple slaves, but noticeable lag between master and
> slave.

I agree with you that we have sync/async option in log-shipping.
Also, we could have another setting - synchronous-shipping and
asynchronous-flushing. We won't lose transactions if both servers are
down at once and can avoid delays to flush wal files into primary's disks.

As for multiple slaves, we could have a cascading configuration;
WAL receiver also delivers WAL records to other servers.
I think it is simple that the postgres core has only one-to-one replication
and multiple slaves are supported by 3rd party's WAL receivers.

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center