Re: Improving Availability

Hi Scott, hi Richard,

On 14.12.2005, at 17:30 Uhr, Scott Marlowe wrote:

> This setup I'm talking about would have pgpool on each db server.
>
> If you meant pgpool running on both application servers, that would
> work
> fine with slony in the background and pgpool in load balancing
> mode, or
> with pgpool doing the replication.

Okay, just that I get this right (have to write a business paper on
that and they will take me by the word ...):

Setup would be:

Machine 1:
- web server
- application server connecting to "localhost --> pgpool"
- PostgreSQL installed and accessed only via pgpool
- pgpool installed and knowing of machine 1 and machine 2
(replication mode)

Machine 2:
- web server
- application server connecting to "localhost --> pgpool"
- PostgreSQL installed and accessed only via pgpool
- pgpool installed and knowing of machine 1 and machine 2
(replication mode)

If one machine fails, the replication is cut off, and pgpool works
with the other machine. Okay so far.

The applications only know the connection to the local pgpool, so
they are fault tolerant as far as pgpool accepts requests.

If one machine fails, the service is not down because as far as all
the services on the remaining machines are working properly. To get
everything back, we will have to shut down all apps and all
databases, sync the db data directories from the working machine to
the machine that has failed, start the dbs, start pgpool, start the
applications.

Everything correct?

cug