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From "Hawkeye I. King" <hawk...@aruke.com>
Subject Re: Database load balancing?
Date Tue, 25 Feb 2003 05:54:25 GMT

    It seems you've confirmed my suspicions that database server load
balancing is not a mature, open-source technology.

    I think Mr. Einfeldt's suggestion of 4 apps to 2 DBs, where one DB
instance is shared by two apps, might be the best.  Since load is balanced
among the app servers, hopefully load to the back-end will be similarly
balanced.  Fail over between the two DB instances could also be implemented,
perhaps by a hardware proxy...

Thanks for the feedback,

Hawkeye King


----- Original Message -----
From: "Ralph Einfeldt" <ralph.einfeldt@uptime-isc.de>
To: "Tomcat Users List" <tomcat-user@jakarta.apache.org>
Sent: Monday, February 24, 2003 7:54 PM
Subject: RE: Database load balancing?


It depends on your requirements.

For read only load balancing to achieve more performance
you might also consider to use replication:

http://gborg.postgresql.org/project/pgreplication/projdisplay.php

This way you could for exapmle setup 4 instances of
tomcat and 2 instances of postgreSQL where one db instance
is shared by two tomcats.

This is no true loadbalancing, but might give you
enough power through the use of serveral db instances.

The main drawbacks against true load balancing are:
- no simple fail over (you would have to implement on your own)
- no load based switching between databases. (The
  connectiones between the tomcat instances and
  the databases are rather static)


You migh also read the following article
http://conferences.oreillynet.com/presentations/os2002/johnson_darren.pdf

with pointers to other replication solution to postgreSQL.



> -----Original Message-----
> From: Hawkeye I. King [mailto:hawkeye@aruke.com]
> Sent: Monday, February 24, 2003 11:39 AM
> To: Tomcat Users List
> Subject: Database load balancing?
>
> Does anyone have a clue about load balancing read-only
> database requests to PostgreSQL?  I'm developing a
> data-intensive application that requires scalability,
> not just from Tomcat, but from Postgres as well.
> I will use hardware load balancing to Tomcat, but I cannot
> do the same to a database using persistent connections.
>
> The only thing I've seen (after several days of searching) is
> DBBalancer, an alpha release load balancer with no JDBC support.
>

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