[KLUG Members] Postgres Cluster

[Andrew Eidson]

Thanks.. I guess what I was describing in an MS SQL world is a Fail-over
Cluster. Which I would love to get working in Postgres first before I
attempt a Cluster where all data is replicated on both machines but only
part of the data is processed by a specific machine. 

-----Original Message-----
From: members-bounces at kalamazoolinux.org
[mailto:members-bounces at kalamazoolinux.org] On Behalf Of Dirk H Bartley
Sent: Tuesday, July 19, 2005 10:28 AM
To: The main KLUG mailing list.
Subject: Re: [KLUG Members] Postgres Cluster

I wouldn't evan use the word cluster to describe a backup situation like
this.  It's splitting hairs a bit.  I would only use the word cluster to
describe a situation where each machine has live data ( such as the one
described ) and each machine is accepting querries (unlike the one
described).  The application being used could be responsible for only
performing update querries against a machine which would be a master.
Clustering with multiple masters get's really sticky because of record
locking.  Man what a pain.  I could not evan imagine trying to lock the
same record on 1 or many replicants for a multiple master configuration.

I use unidata and would definitely not call what I do a cluster.
Unidata keeps a transaction log.  I periodically (every 15 minutes)
rsync the transaction log over to a backup unidata server.  If there is
a major catastrophe on the main server, a script can be run to play the
transacitions into the backup from the last night.  The maximinum amount
of transactions I can lose is 15 minutes worth.

I like talking word semantics. So I ask the question is ldap with
replicant servers an ldap "cluster".  I'd say yes, but no-one I have
ever heard has called ldap servers with replicants a cluster.  Why???
Does the dictionary say that a cluster must be on a data repository to
some xxx standard??  I would guess not.  Language can be fun.

Unfortunately, I have never attempted to cluster postgres servers, so an
answer to your direct question is absent from my experience.

Dirk

On Tue, 2005-07-19 at 09:35 -0400, Andrew Eidson wrote:
> Hey all.. I was looking at the Postgres documentation and their definition
> of a Database Cluster is different from what I am use to with MS SQL. The
> definition in the manual basically states a cluster is multiple databases
> run by a single instance of Postgres. A cluster in the terms of my
thinking
> is a setup of multiple SQL installs/machines that replicate from a Main
> point incase one machine/install fails the next machine takes over until
the
> primary machine can be repaired and then replicate the data from the
backup
> machine before it becomes live again.. can postgres do this and if so can
> someone point me to documentation on it. 
> 
> Thanks
> 
> Andrew Eidson
> 
> _______________________________________________
> Members mailing list
> Members at kalamazoolinux.org
> 

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