Re: High-Availability Question

> I hava a db server (mysql) in my web application, it include 550
> tables and about 100000 rows in each table. Now, I want to change the
> db server to postgresql and construct a HA environment.
>
> I have two 2U servers to build postgresql server (one is master, the
> other is slave), and two 1U servers for any purpose about the ha
> environment. And I expect to use the FreeBSD as the operation system.
>
> My request is, when a server fail (no matter the master or slave), the
> web server can still access (read/write) the database correctly.
>
> I have three ideas about the HA environment, does anyone give me some advices?
> Or guide me to learn more advanced ideas. Thanks. :)
>
> First idea:
> I install the pgpool on each web server (the web server farm include
> 16 web servers), and configure the pgpool as replication mode. The web
> application (written by php) access to the db server through the local
> pgpool daemon.
> The idea sounds a little unusual, dose it seems workable?
> I just use very simple sql statment in the web application, no any
> complex statment.

This is not unusual and actualy I think it's a good idea. Also you
could enjoy the advantage of the load-balance capability of pgpool in
this case.

> Second idea:
> I install the pgpool and linux-ha on the two 1U server, and configure
> the pgpool as replication mode. The web application access to the db
> server through the pgpool daemon.

I'm not familiar with linux-ha so have no idea if this works or not.

> Third idea:
> I install the Slony-I, linux-ha and postgresql on the same server of
> the two 2U servers. The web application access to the db server
> directly and without pgpool.

I'm not sure what would happen with this configuration.
--
Tatsuo Ishii
SRA OSS, Inc. Japan