[Pacemaker] heartbeat vs. corosync installation confusion

[Dennis Jacobfeuerborn]

Hi,
I'm planning to setup a redundant storage system using centos5, pacemaker, 
corosync, drbd, nfs and I'm wondering about the status of heartbeat vs. 
corosync when it comes to the installation of the pacemaker subsystem of 
the setup.

 From what I've learned lurking on the ML heartbeat is considered a 
"legacy" part of the stack that is supposed to be replaced by corosync so 
my plan is since this is a new setup to not bother with heartbeat and go 
straight for the new corosync route. When I install pacemaker though (using 
the clusterlabs rpms) it seems to not only pull in heartbeat automatically 
but also enable its init script by default. Is this intended?
Can I safely disable the heartbeat init script when using corosync?

Why am I required to install heartbeat when I want to use corosync in its 
place?

Regards,
   Dennis