Re: Replication

Darren,
Given that different replication strategies will probably be developed
for PG, do you envisage DBAs to be able to select the type of replication
for their installation? I.e. Replication being selectable rther like
storage structures?

Would be a killer bit of flexibility, given how enormous the impact of
replication will be to corporate adoption of PG.

Brad

>>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<<

On 2/8/02, 5:29:22 AM, Darren Johnson <darren(dot)johnson(at)cox(dot)net> wrote
regarding Re: [HACKERS] Replication:

> >
> > The problems with two stage commit type approches to replication are

> IMHO the biggest problem with two phased commit is it doesn't scale.
> The more servers
> you add to the replica the slower it goes. Also there's the potential
> for dead locks across
> server boundaries.

> >
> > 2) All of the databases must be able to communicate with each other at
> > all times in order for any edits to work. If the servers are
> > connected over some sort of WAN that periodically has short outages this
> > is a problem. Also if your using replication because you want to be
> able
> > to take down one of the databases for short periods of time without
> > bringing down the others your in trouble.

> All true for two phased commit protocol. To have multi master
> replication, you must have all
> systems communicating, but you can use a multicast group communication
> system instead of
> 2PC. Using total order messaging, you can ensure all changes are
> delivered to all servers in the
> replica in the same order. This group communication system also allows
> failures to be detected
> while other servers in the replica continue processing.

> A few of us are working with this theory, and trying to integrate with
> 7.2. There is a working
> model for 6.4, but its very limited. (insert, update, and deletes) We
> are currently hosted at

> http://gborg.postgresql.org/project/pgreplication/projdisplay.php
> But the site has been down the last 2 days. I've contacted the web
> master, but haven't seen
> any results yet. If any one knows what going on with gborg, I'd
> appreciate a status.

> Darren

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