Running Multiple Postmasters
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
(972) 813-5004
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