RHEL

Pacemaker has been available as part of RHEL since 6.0 as part of the High Availability (HA) add-on.

While this is an important step, it has created some challenges, because:
 * Red Hat funds much of Pacemaker's development, so we prefer to make packages available via their official channels rather than the community site
 * Pacemaker is currently listed as Tech Preview (TP) and therefor unsupported by Red Hat
 * The HA add-on costs money

Why should I pay for something if I still wont be supported?
Valid question, but there are still plenty of other software (such as corosync openais, cman, and fencing agents) that is supported if you buy the add-on. You also get a warm fuzzy feeling for supporting continued Pacemaker development.

Even if the lack of support is a deal breaker, consider buying at least one copy of the add-on. You'll get software updates for the entire stack and it helps Red Hat gauge the demand for Pacemaker - which could conceivably help it become supported sooner.

When Community Support is Enough
If you're really not interested in support, you have a number of options available:
 * 1) Install from the RHEL install media
 * 2) Install from the Scientific Linux repos
 * 3) Download and rebuild the necessary SRPMs from the Red Hat FTP server

To take the Scientific Linux approach:

Add it as a disabled repository:

cat < /etc/yum.repo.d/slinux.repo [scientific-linux] name=Scientific Linux baseurl=http://ftp.scientificlinux.org/linux/scientific/6/x86_64/os/ enabled=0 EOF

And then install Pacemaker by running: yum install --enablerepo=scientific-linux pacemaker

Yum then takes care of all the dependencies and (somehow) only uses the pacemaker/corosync/etc packages from Scientific Linux while the rest comes from Red Hat.