----- On 12 Jun, 2015, at 6:36 PM, Dan Storm storm@err0r.dk wrote:
Hello.
I just saw this YouTube video: https://www.youtube.com/watch?v=hYSGsgIyshs It was really informative and it seems like a simple and easy setup.
Now, I have a few questions which is regarding maintaining a Galera Cluster, which I hope to get some answers on.
1. A cluster should have an odd number of nodes to avoid brain split.
Split brain is avoided with 3+ nodes. You won't get split brain with even nodes as the quorum is 1/2 + 1 nodes. i.e. It does mean 1/2 the nodes can't form a quorum.
In case I hit the wall with insufficient disk space and I need to scale up my servers, which steps would be the appropriate? My initial thoughts would be taking down one node at a time and add a larger node, what for it to have replicated from the other nodes. Would the - now even numbered of nodes - handle this?
Bit vague. Stick to your even (>2) nodes.
And what will have when I do this to the bootstrapped server (the one the others connects to)?
same as any cluster initialisation
2. According to the video, a slave replication of the cluster would be a way of securing my data in case of disaster. Would creating dumps regularly not suffice? And secondly, in case of hardware failure on one of the nodes, bringing in a new node (probably asking the same as before) would hopefully just replicate the data when it joins again?
Look up the important conceptual difference between backup and DR. Make sure what you have meets your requirements for doing a restore (related to backup) in a workable time covering the business requirements. Backup covers things like dumb user did a DELETE without a where clause, SQL injection and general data corruption that will affect all nodes. The DR recovery mechanism (hardware failure etc... ) covers your calculated business and technical risks. Hint, you many need more that one mechanism. -- -- Daniel Black, Engineer @ Open Query (http://openquery.com.au) Remote expertise & maintenance for MySQL/MariaDB server environments.