The Blackhole storage engine represents the same general characteristics of it’s celestial namesake. Information is accepted via DML statements, however this information cannot be retrieved as it is never actually stored.
• Very fast
• No disk space requirements
• Ideal for benchmarking
• Row level locking
• Does not support transactions
• Does not store data
While it may seem that this table is impractical in a production MySQL system it does serve specific benefits in isolated cases. The two primary reasons for using Blackhole are for security and for replication performance. When important information is stored in the MySQL table outside a firewall for example credit card details on a public website, the use of Blackhole and replication can ensure this data is never actually stored in the external database, accessible for possible attack. When used in replication, it can be used in a relay slave to speed up performance. It may also be used for selective tables on a master or slave servers to preserve the structure of the database schema and DML statements, however the data is never stored.