Re: Data Replication

On Dec 10, 2008, at 2:18 PM, Rutherdale, Will wrote:

> Hi.
>
> I am trying to determine what kind of data replication is currently
> available in PostgreSQL.  This is for purposes of examining
> capabilities
> of PostgreSQL as compared to other RDBMSs.
>
> I attempted some searches in various areas and came up with a
> bewildering array of results but no clear answer.
>
> a)  Slony-I provides master/slave data replication (3rd party product
> but FOSS)
> b)  PGCluster for Multi-master data replication, also 3rd party add-on
> tool, also FOSS.
> c)  Postgres-R for multi-master data replication, appears to be a code
> fork of PostgreSQL
> d)  Support for data replication in core PostgreSQL engine coming
> up, as
> announced in this article in June 2008:
> http://scale-out-blog.blogspot.com/2008/06/postgresql-gets-religion-abou
> t.html
>
> By contrast, when I search a similar question about MySQL, I get a
> clear
> answer that both master/slave and multi-master data replication are
> supported directly by the core engine.

Kinda.

> Could somebody please help me sort this out?  I would like to know
>
> i)  What is the current available support for data replication in
> PostgreSQL?

There's not really such a thing as one true replication solution. There
are a wide range of different requirements and tradeoffs. HA is
different
to load balancing is different to geographical distribution and so on.

http://www.postgresql.org/docs/8.3/static/high-availability.html covers
some of the tradeoffs of different approaches.

Log shipping, skytools and pgpool are the three main methods I can
think of that you didn't mention.

http://wiki.postgresql.org/wiki/Replication%2C_Clustering%2C_and_Connection_Pooling
  has
others, and a bunch of references.

> ii)  Does anybody have experience with these tools they could share?
> iii)  Is data replication planned for an upcoming release of
> PostgreSQL,
> and if so what are the exact features and when is the release
> expected?

See http://www.postgresql.org/docs/8.3/static/warm-standby.html for
the current in-core support for log-shipping based replication.

Cheers,
   Steve