I've finally built my first cluster on rhel5 using gfs2 and drbd8 :-D
drbd makes a network raid1 between two physical distinguished block devices (eg. internal disks of two servers) and from the release 8.0 it supports the active/active configuration.
gfs2 permits to the two server machines a concurrent mount of the network replicated drbd device.
rhel5 is the OS I've installed on the two machines.
Practically with this stuff the servers share …