Blackhole is available as of MySQL version 4.1.11. The BLACKHOLE storage engine operates just like the MyISAM engine except that it won't store any data. You might use this engine to gauge the overhead incurred by logging, because it's still possible to log the queries even though data will not be stored

The BLACKHOLE storage engine isn’t enabled by default, meaning you need to include the option --with-blackhole-storage-engine at configuration time to use it.

Blackhole Engine Related FAQs