Re: [HACKERS] Proposal for a cascaded master-slave replication system - Mailing list pgsql-general

Jan,

I am wondering if you are familar with the work covered in 'Recovery in
Parallel Database Systems' by Svein-Olaf Hvasshovd (Vieweg) ? The book is an
excellent detailed description covering high availablility DB
implementations.

I think your right on by not thinking smaller!!

Jordan Henderson
On Wednesday 12 November 2003 10:45, Jan Wieck wrote:
> Hans-Jürgen Schönig wrote:
> > Jan,
> >
> > First of all we really appreciate that this is going to be an Open
> > Source project.
> > There is something I wanted to add from a marketing point of view: I
> > have done many public talks in the 2 years or so. There is one question
> > people keep asking me: "How about the pgreplication project?". In every
> > training course, at any conference people keep asking for synchronous
> > replication. We have offered this people some async solutions which are
> > already out there but nobody seems to be interested in having it (my
> > person impression). People keep asking for a sync approach via email but
> > nobody seems to care about an async approach. This does not mean that
> > async is bad but we can see a strong demand for synchronous replication.
> >
> > Meanwhile we seem to be in a situation where PostgreSQL is rather
> > competing against Oracle than against MySQL. In our case there are more
> > people asking for Oracle -> Pg migration than for MySQL -> Pg. MySQL
> > does not seem to be the great enemy because most people know that it is
> > an inferior product anyway. What I want to point out is that some people
> > want an alternative Oracle's Real Application Cluster. They want load
> > balancing and hot failover. Even data centers asking for replication did
> > not want to have an async approach in the past.
>
> Hans-Jürgen,
>
> we are well aware of the high demand for multi-master replication
> addressing load balancing and clustering. We have that need ourself as
> well and I plan to work on a follow-up project as soon as Slony-I is
> released. But as of now, we see a higher priority for a reliable master
> slave system that includes the cascading and backup features described
> in my concept. There are a couple of different similar product out
> there, I know. But show me one of them where you can failover without
> becoming the single point of failure? We've just recently seen ... or
> better "where not able to see anything any more" how failures tend to
> ripple through systems - half of the US East Coast was dark. So where is
> the replication system where a slave becomes the "master", and not a
> standalone server. Show me one that has a clear concept of failback, one
> that has hot-join as a primary design goal. These are the features that
> I expect if something is labeled "Enterprise Level".
>
> As far as my ideas for multi-master go, it will be a synchronous
> solution using group communication. My idea is "group commit" instead of
> 2-Phase ... and an early stage test hack has replicated some update 3
> weeks ago. The big challange will be to integrate the two systems so
> that a node can start as an asynchronous Slony-I slave, catch up ... and
> switch over to synchronous multimaster without stopping the cluster. I
> have no clue yet how to do that, but I refuse to think smaller.
>
>
> Jan