On Wed, Feb 20, 2008 at 2:10 PM, John Evans <admin at kilnar.com> wrote:
>  All of the documentation that I've found is for replicating a single
>  database to another postmaster instance (locally or remotely). I have
>  been unable to find anything that allows me to extrapolate how to do 20
>  databases from a postmaster to 20 databases on another postmaster.
>
>  If anyone has any pointers on the best way to do this, I would
>  appreciate it.

Replicating 20 database is the same as replicating 1, you just need 20
times as many configuration files or scripts and 20 slon daemons
running per database.

>  Also, from my reading, I have been lead to believe that a single instance
>  of 'slon' will be running for each database/node. Is this correct? Does
>  this mean that I'll have 20 instances of slon running on each server? If
>  this is the case, is the memory footprint of the process known? I can
>  find out on my own, but if someone knows off the top of the head, I'd
>  appreciate the information.

Yes, you need 1 instance of slon per database node, so if you have 20
databases to replicate from one node to another, you will have 40 slon
daemons running.

Also note that each slon appears to keep 4 connections open to the
database it's monitoring and 1 connection open to the other node, so
with 20 databases and 2 nodes, you'll have about 100 slony related
database connection open all the time.

On my Fedora 8 32bit test system, ps reports a single slon instance as
using about 70MB VSZ and 4-5MB RSS. The amount of memory used seems to
be more on some CentOS 64bit systems I've checked.

-Dave