Re: [GENERAL] Binary Replication and Slony

I have applied the attached documentation improvement to better
highlight Slony's abilities.

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Brad Nicholson wrote:
> On 10-09-20 12:49 PM, Bruce Momjian wrote:
> > John Cheng wrote:
> >> Congrats on the 9.0 release of PostgreSQL. One of the features I am really
> >> interested in is the built-in binary replication.
> >>
> >> Our production environment has been using PostgreSQL for more than 5 years
> >> (since this project started). We have been using Slony-I as our replication
> >> mechanism. I am interested to find out the pros and cons of Slony vs the
> >> built-in replication in 9.0. Based on what I understand:
> >>
> >> * Slony has a higher overhead than the binary replication in 9.0
> >> * When using Slony, schema change must be applied via slonik (in most cases)
> >> * Unfortunately, IMO it is easy to make a mistake when applying schema
> >> changes in Slony, fortunately, it is easy to drop and recreate the
> >> replication sets
> >> * Slony is an asynchronous replication mechanism
> >> * Slony allows you to replication some tables, while ignoring others
> >>
> >> * PostgreSQL 9.0 with hot standby& streaming replication is an asynchronous
> >> replication mechanism
> >> * Overhead is low compared to Slony
> >>
> >> Are there some cases where it is better to use Slony, for example, when you
> >> must specifically exclude tables from replication? I believe our system will
> >> be better off using the built-in replication mechanism of 9.0, and I am
> >> guessing most people will be in the same boat.
> > You have summarized the differences well. Streaming replication has
> > lower overhread, but doesn't allow per-table granularity or allow
> > replication between different versions of Postgres.
> >
>
> Slony will also allow you to:
>
> -run custom schema (like extra indexes) on replicas
> -replicate between different hardware architectures and OS's
> -run lengthy queries against replicas having to worry about trade offs
> surrounding query cancellation vs standby lagging.
> -switch roles of two nodes without entering a degraded state or worrying
> about STONITH. If you switch roles in a controlled manner, both nodes
> remain in the cluster. Slony prevents writes against the replica.
>
> I do agree that for most, Slony is overkill and streaming replication
> and hot standby will be the better choice.
>
> --
> Brad Nicholson 416-673-4106
> Database Administrator, Afilias Canada Corp.
>
>
>
> --
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--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +