For /etc/fstab on Linux-HA, you typically would not change /etc/fstab as part of the resource start. Normally what you would do is list all the mount-points you may have, but ones that are not always mounted list with "noauto". For example:
/dev/drbd0 /shared ext3 defaults,noauto,noatime 0 0
/dev/drbd1 /var/lib/pgsql ext3 defaults,noauto,noatime 0 0
At boot time those file-systems will not be mounted. Then, to bring those file-systems up you would list a resource like:
Additionally, you may wish to look at drbdlinks (probably available in your distro) which manages links to DRBD file-systems. However, I don't think you want to make /etc/fstab a drbdlink...