Re: Running Multiple Postmasters

Hello,

We do it all the time at Command Prompt. That is how we do the managed
shared hosting. Every customer gets a private
data directory that is on its own TCP port.

J

Clay Luther wrote:

> I am wondering if it is possible, or even advisable, to run two
> postmasters on a single system.
>
> For example, we have an embedded system with a normal runtime
> partition (called the "A") in which the PGDATA is /var/lib/pgsql/data.
> We also have a offline partition which is a copy of the runtime
> partition, but is mounted under /partB -- PGDATA here is
> /partB/var/lib/pgsql/data.
>
> During upgrades, we will alter the installation on the B partition,
> then swap the paritions after a reboot.
>
> However, during upgrades, we may need to migrate data from the A
> partition databases to the B partition databases.
>
> For database migrations, I was hoping I could do the following
> (remember, a postmaster is already running on /var/lib/pgsql/data):
>
> 1) Alter the the postgresql.conf of the B partition PGDATA, setting
> the tcp/ip port to 54321.
> 2) Start the "B" postmaster, pg_ctl -D /partB/var/lib/pgsql/data start
> 3) Use ODBC/JDBC to perform necessary migration from A databases to B
> databases.
> 4) pg_ctl -D /partB/var/lib/pgsql/data stop
> 5) Set B postgresql.conf tcp/ip port to 5432.
> 6) Reboot (higher level systems will automatically swap the A and B
> partitions, so B becomes A and A becomes the new B).
>
> Conceptually clear, but I wanted to know if there was anything I
> needed to be worried about.
>
> Thanks.
>
> ---
> Clay
> claycle(at)cisco(dot)com <mailto:claycle(at)cisco(dot)com>
> (972) 813-5004
>
>
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