I used DRBD before it was cool (before it was added into the kernel), and it works great for highly available directories like home dirs, which was my use case.

I used DRBD before it was cool (before it was added into the kernel), and it works great for highly available directories like home dirs, which was my use case. Even then it was pretty solid, and it's very similar to using a high end NAS product like NetApp or EMC with automatic failover, except you don't have to shell out $100K+++ for it. If you used it for a database then everything committed to disk is immediately available on the partner, which you can spin up instantly with some scripts. And look, your transaction log is exactly where you left it! With a database and built-in replication you could go either way, but there are some applications with persistency that you need to make highly available, and that's another area DRBD would shine.