Re: PostgreSQL in Shared Disk Failover mode on FreeBSD+CARP+RAIDZ

It's hard to say Robin, I'm still in testing.
At the beginning I'd say very low ... probably something between 2000
and 5000 transactions a day (even harder to imagine how this load it's
gonna be distributed within 24 hours)?!

Thanks for your reply.

On Tue, 2010-12-21 at 08:02 +0000, robin wrote:
> How much data and what sort of write rates do you actually expect?
>
> Cheers,
> Robin
>
> On Tue, 21 Dec 2010 02:23:25 +0100, snoop@email.it wrote:
> > Hi everybody,
> > I'm trying to figure out a way to setup a PostgreSQL HA cluster
> solution.
> >
> > For the record:
> > - I've already tried pgpool-II 2.x in Synchronous Multi Master
> Replication
> > mode and I was satisfied by it's functionality but concerned about
> having
> > the same data growing on several nodes
> > - I've upgraded to pgpool-II 3.0.x on FreeBSD (from ports) but it's very
> > buggy at the moment
> > - I don't like the idea of having fixed size (16 megs regardless of the
> > committed transaction number!) WAL logs often "shipped" from one node to
> > another endangering my network performance (asynchronous replication)
> >
> > I've done some research and I've an idea of different possible
> solutions,
> > but I'd honestly like to implement it using CARP in a "Shared Disk
> > Failover"
> > fashion.
> > Unfortunately this doesn't really seem to be a common way according to
> the
> > very limited information available on the net and that's why I'm going
> to
> > ask here.
> >
> > My idea: two nodes (i386) with FreeBSD 8.1 and PostgreSQL 9.0.2, CARP
> > providing network failover and a shared data dir on a RAIDZ solution.
> I'm
> > pretty sure that CARP would do the job properly indirectly avoiding even
> > the
> > dangerous writing on the data dir from both nodes at the same time (that
> > would apparently badly screw up the DB) by redirecting any network
> > connection to the active DB and to him only.
> >
> > BUT ... I'm seriously concerned about the already active connections
> client
> > <-> server during the failover.
> > Example:
> >
> > client A connects to server A
> > server A fails so does the client A connection
> > CARP redirects any upcoming connection to the DB to server B now
> > client A reconnects and is now operating on server B
> > THEN
> > server A comes back up
> > CARP now obviously redirects any new connection to the DB to server A
> again
> > client B connects to server A
> > what about the existing connection of the client A to the server B?
> there's
> > an existing connection state between client A and server B
> > now there's the chance that a transaction can be committed on the server
> B
> > while there's someone else operating on server A too!
> >
> > I understand that in a server that doesn't commit many transaction but
> is
> > mainly answering queries this could be a remote situation but it can
> > probably happen.
> > Please correct me if I'm wrong (as I really hope to be).
> >
> > Did anyone here try such a configuration by any chance?
> >
> > Many thanks in advance for your time.
> >  --
> >  Caselle da 1GB, trasmetti allegati fino a 3GB e in piu' IMAP, POP3 e
> SMTP
> > autenticato? GRATIS solo con Email.it: http://www.email.it/f
> >
> >  Sponsor:
> >  Paghe e stipendi, consulenza e collocamento, tutto con Emailpaghe!
> Provalo
> > gratuitamente fino al 31/12/2010
> >  Clicca qui:
> http://adv.email.it/cgi-bin/foclick.cgi?mid=10682&d=20101221




 --
 Caselle da 1GB, trasmetti allegati fino a 3GB e in piu' IMAP, POP3 e SMTP autenticato? GRATIS solo con Email.it
http://www.email.it/f

 Sponsor:
 MisterCupido.com crea i tuoi regali personalizzati ai prezzi pi� bassi del web... e questa settimana ci sono pi�
scontiche mai! 
 Clicca qui: http://adv.email.it/cgi-bin/foclick.cgi?mid=11031&d=22-12