Cascading Replication

Cascading Replication is now part of PostgreSQL 9.2, thanks to Fujii Masao.

The idea is that a streaming replication standby can also stream data onto other standbys. This allows a complex network of interrelated servers to fulfil the roles of High Availability, High Durability, Distributed data access capacity and Reporting requirements.

You can set up chained configurations like A -> B -> C.

or more complex arrangements like
......A
....B....E
..C.D...F.G

This should make it much easier to reduce bandwidth for intercontinental replication.

Nice thing is that Hot Standby feedback works across the whole cluster, so you easily manage the interrelationships between servers.

CHAR(11) Conference Success

Finally recovered from attending CHAR(11) in Cambridge, UK. 2 complete days of Clustering, High Availability and Replication talks from various experts.

We had 15 talks from 14 speakers from US, Japan and from 8 European countries, including the keynote from Jan Wieck. Attendees came from US and all across Europe, many of whom could give detailed talks themselves. There's always next year...

The most amazing thing were the comments we received from attendees. Every talk was packed solid, and judging by the seats alone it seems almost everybody went to all the talks - for the whole talk. I don't recall a conference having such a good attendee rate, not even CHAR(10) last year.

Based on that, it looks pretty certain that we'll run CHAR(12) next year. We did discuss Japan for CHAR(12) but that's not going to be as easy as we'd hoped. Let's see how that goes.

I'm pleased with how everything ran, so a big thanks to the organising team.

Thanks very much to Koichi Suzuki for visiting again. The panel discussion between Postgres-XC, MGRID and Greenplum was very enlightening.

Thanks to all the speakers and attendees also.

Five Nines

In High Availability we talk about "Five Nines" meaning 99.999% availability. I like to joke that a badly configured system has "Nine Fives" availability or 55.555555% availability.

With a sensible architecture and good operational controls, data can be made "Five Nines" safe with PostgreSQL 9.1.

I was reminded today that "Five Nines" had another meaning in an earlier age. Wilfrid Owen's wartime poetry describes

And towards our distant rest began to trudge.
Men marched asleep. Many had lost their boots
But limped on, blood-shod. All went lame; all blind;
Drunk with fatigue; deaf even to the hoots
Of tired, outstripped Five-Nines that dropped behind.

meaning artillery shells falling away from the target of the front line troops.

The poem ends with an exhortation to learn from earlier mistakes

My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori.

"How sweet and fitting it is to die for one's country"

I'm sure there's a modern message there, but I'll leave that up to you.

Gentlemen, Start your Engines

The racing season is upon us. We have both the Le Mans 24 hour race and the Indy 500 coming in the next month, both long distance, high speed motor racing events.
http://www.indianapolismotorspeedway.com/indy500/
http://www.lemans.org/

We also have the beta of PostgreSQL 9.1 and associated tools.

Just like motor sport, a 5 minute engine test proves very little. Only good solid usage at high levels of performance will prove whether the engine is good enough to be world class.

Just like a race, we have deadlines and we must remember we aren't the only people in the world producing database software. The deadline is more important this year because we are attempting to cut the time of the beta cycle down by weeks and months.

The PostgreSQL project needs you to start your engines. Start testing PostgreSQL 9.1 as soon as possible and take it to the very limits of durability and performance.

Make the tests run for 500 miles and/or 24 hours. Report the results, in detail.

Do it. Do it now.