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

Jan Wieck wrote:
> Dear community,
>
> for some reason the post I sent yesterday night still did not show up on
> the mailing lists. I have set up some links on the developers side under
> http://developer.postgresql.org/~wieck/slony1.html
>
> The concept will be the base for some of my work as a Software Engineer
> here at Afilias USA INC. in the near future. Afilias is like many of you
> in need of reliable and performant replication solutions for backup and
> failover purposes. We started this work a couple of weeks ago by
> defining the goals and required features for our usage of PostgreSQL.
>
> Slony-I will be the first of 2 distinct replication systems designed
> with the 24/7 datacenter in mind.
>
> We want to build this system as a community project. The plan was from
> the beginning to release the product under the BSD license. And we think
> it is best to start it as such and to ask for suggestions during the
> design phase already.
>
> I would like to start developing the replication engine itself as soon
> as possible. And as a PostgreSQL CORE developer I will sure put some of
> my spare time into this as well. On the other hand there is absolutely
> no design other than "they mostly call some stored procedures" done for
> the frontend tools yet, and I think that we need some real good admin
> tools in the end.
>
> I look forward to your comments.
>
>
> Jan
>

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.

I just wanted to mention that because personally I don't have the
impression that an additional async project is worth the effort.

Note: This does not mean that it is bad to have one more product ;).

    Cheers,

        Hans


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