I am running fop2 on a FreePBX High Availability setup.
There are a few things you need to do to make it work.
Fop2 installs config files into /usr/local/fop2, which is a directory that doesn't get synced across the HA cluster. You have to create one that does. E.g. /drbd/spare/fop2
-Copy contents of /usr/local/fop2 into /drbd/spare/fop2.
I initially chose /etc/asterisk/fop2, but permissions get screwed up on this frequently, so I chose /drbd/spare/fop2.
The server binary and the license file should however reside in /usr/local/fop2, so don't copy those over.
-Make sure that your new directory has read, write and execute permissions for the Asterisk user. The contents of the directory must be read and writeable by the Asterisk user as well.
-Add a -c option to /etc/sysconfig/fop2 to sync the files to drbd/spare/fop2 (or whatever directory you have picked).
E.g.: OPTIONS="-d -i em1 -c /drbd/spare/fop2/"
em1 is what my network interface is called, yours might be different, e.g. eth0
-Edit /var/www/html/fop2/admin and change line $SQLITEDB=[i]"/usr/local/fop2/fop2settings.db"; to $SQLITEDB="/drbd/spare/fop2/fop2settings.db"; (or whatever directory you have chosen).
I might have forgotten something, but I think that's it.