We have a mission critical PHP based system that uses a Firebird SQL
back-end. Works brilliantly and has for many years. This is hosted on
a CentOS server with FB 1.5 (will update FB versions soon to later
releases).

Due to high demand, we are going to need to create multiple server
'nodes' for the system using a DNS load balanced setup. As a result,
servers that run PHP will be located in different geographic regions,
sometimes in different countries. The DNS failover capability will
ensure that at least one server is available for any incoming request.

Although this is relatively painless to setup for general PHP/Apache
operation, it isn't as simple with the database. I'd like to adopt a
common approach that MySQL databases & high demand PHP apps seem to do,
and that is that updates to the database are immediately replicated to
all node systems, which have their own separate Firebird database on
them. In this way, each node is self-contained. If a node is down,
however, I need to find a way to identify changes that were made to a
'master' server, that didn't complete replication to a number of slave
node servers.

Is anyone doing this sort of thing in similar technologies that we use?
If so, how have you chosen to do it? Should I build all of this
technology myself, or are there any pre-written systems that do
replication that already are considered 'bullet proof' that I should be
considering evaluation?

Thanks in advance for any feedback.

Myles
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Myles Wakeham
Director of Engineering
Tech Solutions USA LLC
www.techsolusa.com
Phone +1-480-451-7440