[Gluster-devel] Architecture advice

[Martin Fick]

--- On Mon, 1/12/09, Gordan Bobic <gordan at bobich.net> wrote:

Gordon, 

> Not on the client, anyway. But if you're AFR-ing on
> server side, then your client always talks to one server
> anyway. The traditional way to handle server failure in that
> case is to set up Heartbeat or RHCS to fail over the IP
> address resource to the surviving server.
> 
> The TCP connection will reset when the fail-over occurs -
> I'm not sure how gracefully/transparently GlusterFS
> reconnects.
...

1.4 supports an new HA translator that is meant for clients to contact servers that AFR each other.  Like this:


       Client
         |
        HA
       /   \
      /     \
     /       \
Server A   Server B
    |         | 
   AFR       AFR
    | \     / |
    |  \   /  |
    |   \ /   | 
    |    X    |
    |   / \   |
    |  /   \  |
   Vol A   Vol B


> I wasn't aware of there being a HA translator built
> into GlusterFS, but unless you have proper fencing in place,
> failing over IP addresses won't work. Without proper
> cluster fencing in place you can easily find yourself in a
> split-brain situation where both servers think they have the
> same IP address and neither can talk to any of the clients.
> 
...
No need for fencing simply because you now use HA translator.  The assumption in this case is that the servers can still talk to each other but that one server's connection to the clients may have died.  

Any failures on the server side may still warrant a fencing setup, but AFR is not yet setup to work cooperatively with a fencing setup.

> I think you're trying to use a wrong tool for the job.
> Look into something like RedHat Cluster Server.

HA is now the right tool. :)

-Martin