A couple of days ago I attended a lecture about the Drizzle database server .
Drizzle is a re-write of MySQL for use in large web applications. It is only going to run on 64bit platforms because apparently everyone uses 64bit servers – except of course people who are Amazon EC2 customers as the $0.10 per hour instances in EC2 are all 32bit. It’s also designed to use large amounts of RAM for more aggressive caching, it’s being optimised for large RAM at the expense of performance on systems with small amounts of RAM. This is OK if you buy one (or many) new servers to dedicate to the task of running a database. But if a database is one of many tasks running on the machine, or if the machine is a Xen instance then this isn’t going to be good.
There are currently no plans to support replication between MySQL and Drizzle databases (although it would not be impossible to write the support).
The good news is that regular MySQL development will apparently continue in the same manner as before, so people who have small systems, run on Xen instances, or use EC2 can keep using that. Drizzle seems just aimed at people who want to run very large sharded databases.
Now I just wish that they would introduce checksums on all data transfers and stores into MySQL. I consider that to be a really significant feature of Drizzle.