Re: Proposal for a cascaded master-slave replication system - Mailing list pgsql-hackers

Jan,

This is EXACTLY what we have been waiting for (years) :) :) :).
If you need somebody for testing or documentation just drop me a line.

    Cheers,

        Hans



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
>


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