Open Source Database Clusters?

grugruto asks: "A lot of open source solutions are available to scale web sites with clusters but what about databases? I can't afford an Oracle RAC license but can I have something more reliable and fault tolerant than my single Postgres box? I have seen this recent article that looks promising for open source solutions. Do anyone have experiences with clusters of MySQL , Postgres-R, C-JDBC or other solutions? How does it compare to commercial products?"

Comments

Check out Emic Networks

[venom600]

We've been evaluating the Emic application cluster for MySQL and have had pretty good results. It's a new product (so YMMV), but it looks promising.
Emic Networks

Shared storage?

[crstophr]

You can make a High Availability cluster out of most any software if you have some kind of shared storage.

People have used firewire drives connected to two different computers to accomplish this cheaply. Oracle is giving away a cluster filesystem (so they can sell RAC on linux) there is OpenGFS as well for filesystem usage.

Just write some basic monitoring scripts that will bring up your postgress database on the second server should the first one fail. Just make sure those scripts completely take down the old database on the first server in the case of a partial failure. Having two databases try to open the same data would be a really bad thing.

Here are some links to articles that should help:

Overview

Howto

Cluster Filesystem

These are mainly geared for Oracle/RAC, all you need is the firewire shared storage and cluster filesystem. You're on your own to write the monitoring and failover scripts. Hope this helps. --Chris

Re:eRserver

[TheFuzzy]

Well, the .ORG domain runs on PostgreSQL + eRServer, so that's one scalable solution ...

MySQL replication: Flawless (so far)

[allankim]

I've been running a 3-4 node MySQL 3.23.x cluster on Slowlaris 9 since January. It has survived several catastrophic power outages and numerous other insults without a hiccup. Load is fairly light (about 3,000 updates daily and a similar number of queries on each server) so YMMV.

Re:MySQL Replication

[Hamstaus]

Rings? Are you implying *all* servers involved in the replication process could handle writes rather than a master that handles writes and a bunch of slaves that handle all the read access? If this is true, point me to some docs :) That would be too cool.

Here you go.

The part you are probably interested in is this:

You should run your slaves with the --log-bin option and without --log-slave-updates. This way the slave will be ready to become a master as soon as you issue STOP SLAVE; RESET MASTER, and CHANGE MASTER TO on the other slaves.

Note that if you decide to "ring" your server setups, then you are not necessarily helping distribute the load, you are simply creating redundant masters in the case that your primary machine becomes unavailable. Also, you'll have to write your own monitoring scripts. MySQL says they are working on some tools for this... I'm excited to see what they come up with.