Re: PG engine takeover or switch over

On 15.08.2007 21:30, Medi Montaseri wrote:
> I am looking for some suggestions to optimize the following
> problem/solution.
>
> Given two nodes A and B (two computers) in a active-passive mode where A is
> running PG engine,  and B is simply standing by,  and  a common storage
> (twin tailed) ( or from pg_ctl point of view -D /common/data ), I am looking
> for a faster solution during the takeover where A has crashed and B is to
> start PG engine and run with it.
>
> My current solution is to start PG engine which should take little time to
> study the configuration files and /common/data and fork a few childrens. But
> I am still interested in optimizing this start-up cost.
>
> For example, would I gain anything by starting PG engine on both A and B,
> but on B I point it to /common/dummy and during the takeover, I somehow tell
> it to now read from /common/data, for example have two postmaster.conf or
> PGDATA and then use  pg_ctl reload.

Starting up PostgreSQL should be very fast, given no recovery to be done
and decent hardware.

PostgreSQL does not fork a lot unless it is accepting new connections
and if reading a config file is slow on your system, something else is
broken.

In a active/passive setup your should be able to switch over in under 3
seconds. If there was a lot of load on the failed node the recovery
times on the new active node increase. The only thing you can do about
that is getting faster disks..


--
Regards,
Hannes Dorbath