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Re: Question on HA configuration.




On Wed, May 30, 2018 at 02:01:05PM +0500, Muhammad Yousuf Khan wrote:
> Dear Sir,
> 
> As you have mentioned earlier below.
> 
> wtprd0X (search for ‘wtprd0’) - these are front end web server nodes for an
> HA cluster (uses HAProxy in pfSense)
> wtsqlprd01-3 (search for wtsql) - these are 3 MySQL servers for the backend
> of a site in HA
> 
> I can understand the purpose of 3 frontends but how 3 Mysqls are designed
> are they replicating to each other get updated or or is this a enterprise
> cluster.
> Cluster in a sense where you are running multple nodes of MYSQL but
> application sees only one and if any of the instance goes down the other
> stands for backup. is it like.
> 
>  how does the 3 MYsql stack works. ?
> 

There's lots of information here:

https://mariadb.com/blog-tags/high-availability

The basic options for databases are:

- single write master, multiple read-only replicas

- single write which is also single read, with a standby replica
  that can be substituted in case of a disaster

- multiple read/write replicas available simultaneously, but
  performance is often slower because they all need to
  coordinate potential conflicts

- multiple read/write replicas with "sharding", so conflicts are
  less likely

- and then there are combinations of the above.

The information you have given is insufficient to tell which
scenario is happening.

-dsr-