[ClusterLabs] design question to DRBD

[Lentes, Bernd]

----- On Jun 22, 2016, at 8:34 PM, Dimitri Maziuk dmaziuk at bmrb.wisc.edu wrote:

> On 06/22/2016 01:00 PM, Lentes, Bernd wrote:
>> ----- On Jun 22, 2016, at 7:17 PM, Dimitri Maziuk dmaziuk at bmrb.wisc.edu wrote:
> 
>>> Does your webapp ever write to /srv/www?
> 
>> it does.
> 
> Yeah, OK, it that case you want DRBD so the writes go to both nodes at
> once.
> 
> If you have to use DRBD anyway, then you might as well put DocumentRoot,
> cgi-bin, etc. on DRBD and use ocf:heartbeat:symlink resource to point
> apache to the right directories. Then you have to let the cluster start
> apache after the symlink's updated (after DRBD FS is mounted).
> 
> Similarly you might as well share the database storage the same way and
> let the cluster control the DB server.
> 
> You could do a mix-and-match setup with some bits completely independent
> and running out of init while some other parts are tied to DRBD and
> controlled by the cluster, but that's going to be a pain maintenance-wise.
> 

My idea is to use mysql replication. The ressource agent manages which is master and which is slave.
The database is on a local harddisk on each node.
The IP pointing to the webapp is also a ressource managed by the cluster.
If i have /srv/www on a drbd directories like DocumentRoot, cgi-bin (which are situated under /srv/www)
are automatical on the drbd device.

I'm thinking about starting drbd and the ocfs fs by init. I don't see the strong need having it controlled by pacemaker.
But of course the mix is more difficult to maintain.


Bernd
 

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