Re: Maximum Availability Architecture(MAA) for PostgreSQL

Hi Jay,

I totally agree with you that having a pair hot standbys will be good. What
do you mean by "using WAL shipping in addition to WAL receivers"?According
to the documentation
<http://www.postgresql.org/docs/current/static/warm-standby.html>, if I
configure replication slot, "*the master does not remove WAL segments
until they have been received by all standbys*". In sync replication, if
the standby is down, the transaction will not be able to commit. However,
if we have a pair, as long as 1 of the hot standby is up, the transaction
will still go through.

Hi Jan,

Technically, 2 instance of pg-pool will suffice. However, if we have to
bring 1 instance down for maintenance, there's no standby if the master
crashes.

Anyway, I do realise a tiny flaw in my design, pg-pool is not a
active/active design. It means there's a wasted resource. At least my pair
of hot standbys could serve read queries..

On 8 April 2015 at 20:44, Jan Lentfer <Jan(dot)Lentfer(at)web(dot)de> wrote:

> Am 2015-04-08 10:22, schrieb Wei Shan:
>
>> In the PostgreSQL world, what do you guys think would be the
>> equivalent?
>>
>> Attached is a diagram I have thought of. Clusters of pg-pool2 used to
>> load balance the connection in and for connection failover when a DB
>> crashes. Between master and slave, sync replication is being used for
>> zero-data-loss.
>>
>
> Why do you need 3 pg-pool instances? 2 instances uses watchdog should be
> sufficient?
> And if you plan to use sync replication you need to plan for 3 PostgreSQL
> Servers (a 3rd one that the sync replication can fail-over to).
>
> Regards,
>
>
> Jan
>
>
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--
Regards,
Ang Wei Shan