"Conventional scenarios replicate from one primary node to a secondary, allowing only one more lower-level node after the secondary. With DRBD9 we have created a solution to keep entire networks synchronised. This means that DRBD9 users can add another 9 to the theoretical availability of 99.999%"
DRBD has been around for years and was easy to set up for two servers. If this beta survives, we should soon have the ultimate clustering tool, able to sink dozens of servers, making downtime a thing of the past.