[Linux-cluster] A single server backing up three servers

[brad at bradandkim.net]

> On Mon, Jun 11, 2007 at 01:21:26PM -0500, brad at bradandkim.net wrote:
>> Hi all,
>>
>> I have just begun playing around with redhat cluster and I have a
>> question
>> that I am not finding a straight answer to.   I would like to have one
>> server be a backup to 3 primary servers.   In other words I guess I
>> would
>> have 3 services (db1, db2, and db3) and then a 4th server (db4) that is
>> available to take over for any of the 3 primary servers.   Obviously if
>> 2
>> primary servers fail I am in trouble, but the odds of that are extremely
>> slim.  Is this possible?  Are there caveats?
>>
>
> Yeah you can do this with priority failover domains.  I assume from your
> description that you will want 3 failover domains, one for each
> application.
> You will add two servers for each domain, the primary server which will
> have the
> higher priority and then db4.  Then if anything fails on the main servers
> they
> will failover to db4, and then when they come back up the service will
> failback.
> You will want the "restricted" and "ordered" flag set.  The only caveat
> you have
> already specified, if db4 is down and something fails everything hangs
> since you
> will have lost 2 nodes.  You may want to look into qdisk if you want to
> change
> this behavior slightly.
>
> Josef
>

Thanks Josef.  I will look into qdisk.


Brad Crotchett
brad at bradandkim.net
http://www.bradandkim.net