Re: Load Balancing/Multiple Postgres Machines

Hi Iain,

So what you are saying is that pg pool is used for load balancing and slony
is used for replication? I do have the option programmatically in my code to
distribute the load on the DB as you had mentioned (for example the SELECT
issue you mentioned), so if I was to go down that road would sloany be the
best way to go, or do I still need to use pgpool. Also how easy is sloany to
setup?

Cheers

Adile


-----Original Message-----
From: Iain [mailto:iain@mst.co.jp]
Sent: November 29, 2004 7:22 PM
To: Adile Abbadi; pgsql-admin@postgresql.org
Subject: Re: [ADMIN] Load Balancing/Multiple Postgres Machines


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@postgresql.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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