Hi Michael, thanks for the quick response
Michael Schwartzkopff wrote:
Hi,
no problem to accieve this setup
1) Loadbalancer: Why? Throw it out. Or use LVS with ldirectord as
heartbeat resource.
The loadbalancers are running ldirectord and heartbeat (Version 1), and
are configured solely as loadbalancers and need to stay that way - I
failed to mention this is a solution that is already in place that I am
having to rather work around.
2) Decide if you want to have (a) MySQL and Webserver running on the
same machine of (b) some kind of active/active stetup.
The setup that is required is to have all 3 webservers up and running at
any one time, all connecting to mysql on localhost for reads and the
high availability IP for writes. As it's using Master -> Slave MySQL
replication Web and MySQL should be running on all servers. I may
change the setup to do all reads and writes from the Virtual IP that
heartbeat manages, as I think this may make the whole thing more manageable.
a) Make both into a group together with the IP address of the cluster.
If you want to you can pin the whole group to one node with a location
constraint. But this is not nescessary.
This is where I'm falling apart, I really don't get the setup of the
cib.xml file, what processes interact with it, and how I can use it to
do a daisy chain type setup (server a -> server b -> server c). I know
once I have done this once I will *get it*, it's just getting this first
time out of the way.
b) Make a group with MySQL and IP address 1 and an other group with the
webserver an the IP address of the cluster. Make a colocation
constraint that forbids both groups running on the same node. The
webserver will access the database under the first IP address.
I think this is closer to what I need - although I don't need a floating
IP for the web requests - the separate loadbalancer using ldirectord
takes care of http failing on any server, so I think my cibs.xml needs
to monitor only ping and the MySQL service in order to handle the failover
In both cases you have to think of o good database replication. DRBD is
your friend!
DRBD is something I have had a brief glance at, and does look quite
amazing (it's given me some ideas for future projects), but as I stated
earlier, I don't think this is a situation I can currently use DRBD in.
Have monitoring installed in all ressources and pingd in all nodes. Make
constraints that make the ressoruces running on the "healthiest" nodes.
Again, I think this is set in the cibs.xml if what I have read is
correct, I'm just having a little trouble wrapping my head round it.
Please mail me or the list if you have further questions.
Thanks once more for the time (and detail) in all this
Chris
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