Re: replication choices

Have you read the 8.2 documentation about this:

    http://www.postgresql.org/docs/8.2/static/high-availability.html

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Ben wrote:
> Hi guys. I've inherited a system that I'm looking to add replication to.
> It already has some custom replication code, but it's being nice to say
> that code less than good. I'm hoping there's an existing project out there
> that will work much better. Unfortunately, I'm not seeing anything that
> obviously fits my needs, so maybe somebody here can suggest something.
>
> I've got a single cluster in the datacenter and dozens of remote sites.
> Many of these sites are on unreliable connections to the internet, and
> while they're online more often then not, when their network will go down
> isn't known, and even when it's up, the network isn't that fast.
>
> A vast majority of activity occurs at these remote sites, with very little
> at the datacenter cluster. That said, the datacenter cluster needs to keep
> pretty good copies of most (but not all) of the data at each site.
> Obviously the network unrealiability puts a limit on how up to date the
> datacenter can be, but loosing data is considered Bad. So, for instance,
> restoring the daily backup of each site at the datacenter is too
> infrequent.
>
> Each site will replicate to its own schema in the datacenter cluster, so I
> don't *think* I need a multi-master solution.... but at the same time,
> because data will be coming from multiple sites, simply replaying WAL
> files at the datacenter won't work.
>
> In addition, there will be some data changes made at the datacenter that
> will need to replicate to all of the remote sites as soon as they're
> online. It's ok if data being replicated from the datacenter ends up in a
> different schema at the remote sites than the schema which holds the data
> that will be replicated back to the datacenter.
>
> My current best guess of what to do is create a global schema at every
> database, a local schema at each site, and a schema for each site at the
> datacenter. Then I can use Slony to replicate the global schema from the
> datacenter to each site, and again use Slony to replicate the local schema
> from each site to that site's schema in the datacenter. But I'm not too
> familiar with Slony, and from what I understand, using Slony with bad
> networks leads to bad problems. I'm also not sure that Slony supports
> replicating from multiple sources to the same postgres install, even if
> each replication process is writing to a different schema.
>
> Are there any better options? Or is my Slony idea not so bad?
>
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