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Re: Load Balancing/Multiple Postgres Machines

From: "Iain" <iain(at)mst(dot)co(dot)jp>
To: "Adile Abbadi" <adile(at)minitdrugs(dot)com>,<pgsql-admin(at)postgresql(dot)org>
Subject: Re: Load Balancing/Multiple Postgres Machines
Date: 2004-11-30 02:21:49
Message-ID: 007301c4d683$5bbd29c0$7201a8c0@mst1x5r347kymb (view raw or flat)
Thread:
Lists: pgsql-admin
Hi,

I have been considering this in my spare time for a little while too.

Joshua already mentioned slony and pgpool, and you may want to look at 
heartbeat too, though I don't know if it is strictly neccessary in a 
slony/pgpoos installation. My focus is more on replication for high 
availability and failover than performance.

Replication will involve some overhead so to offset that your application 
must be set up to take good advantage of the load balancing possibilities. 
There is no guarantee that your application will perform faster even if you 
do implement replication.

As such, I don't know of any viable true _synchronous_ replication system 
for postgres, the options listed above seem best suited for async 
replication (using slony) and load balancing of SELECTs (not UPDATE INSERT 
DELETE) using pg pool. If your application has a very heavy SELECT component 
from browsing users (perhaps from a web application) then you may be able to 
have a large portion of your SELECT SQL diverted to the slave database, 
freeing the master to handle all updating of data.

Whether this will help you or not, I don't know. Analyse the options and 
your requirements and test it. If you come up with any good information, I'd 
be very intertested to hear it.

I posted a summary of options as I understood them in the admin section. If 
your search on availabilty and  failover you should find it.

Regards
Iain

----- Original Message ----- 
From: Adile Abbadi
To: pgsql-admin(at)postgresql(dot)org
Sent: Tuesday, November 30, 2004 3:34 AM
Subject: [ADMIN] Load Balancing/Multiple Postgres Machines


Hi all,

Not sure if this has been asked before - it probably has been - but I figure 
its probably just easier if I ask so my question is this:

How easy is it - or rather is it possible to create multiple instances of 
the same db on multiple machines?

We are currently running a very highly used postgres db (Ver 7.2) that eats 
up a lot of cpu time when its heavily used. We recently bought some very 
powerful equipment to accommodate this high use, (currently its on a single 
CPU, 1GB of Ram SCSI server - upgraded to a dual CPU, 4GB of ram SCSI 
server) but my fear is over time this issue is going to haunt me again and 
hardware can only be upgraded so much.

So is it possible to do some level of load balancing in postgres - I would 
love a situation where I could have multiple machines running multiple 
instances of the same db (that are all synced in real-time), where there is 
some smart level of load balancing happening.

So if it is possible is there some instruction info out there to help me 
along my way. Any help or insight would be greatly appreciated.

All the best

Adile 


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