[ale] OCFS2

[Chris Ricker]

On Mon, 20 Mar 2006, Greg Freemyer wrote:

> I thought MySQL supported DB clustering without any underlying FS
> support (ie. drbd/ocfs2/gfs).
> 
> You setup one node as the MySQL master and the other as the slave. 
> MySQL handles the redundancy and failover?

That's two different things

* MySQL Cluster is MySQL's officially supported HA database clustering. 
It's done without shared storage, by keeping the active db in memory at 
all times (so it's only good if you can afford lots of RAM or have small 
databases)

* master / slave is data replication between two separate MySQLs. It's not 
really HA in the usual sense. If the master fails, you're going to have to 
promote the slave manually, redirect clients, etc.

> I've also seen where people used drbd under MySQL, but I don't know
> the pros and cons of the 2 approaches.  To my limited knowledge they
> both seem valid.

drbd + linux-HA + MySQL lets you easily have a small active-passive HA 
setup where if one node dies the other node automatically kicks in and 
continues. Linux-HA floats the IP so clients always hit the active node, 
and deals with starting MySQL only on the active node. drbd mirrors the 
disks so either node can be active and get the same underlying data

MySQL Cluster is more geared towards a larger active-active HA setup. You 
have multiple Storage Nodes which replicate the database between 
themselves. You have multiple Server nodes which are servers accessing the 
Storage nodes; your mysql client connects to the server nodes, which 
connect to the storage node backend. You have a Management Node to 
supervise everything... You can make this cluster as small as one node, 
but obviously you kill all HA aspects by doing so. The architecture really 
gears towards at least 5 boxes for full HA

later,
chris