Percona Server is a branch of MySQL enhanced with additional features.
Disk-oriented
SQL
Shared-Everything
Heaps
N-ary Storage Model (Row/Record)
Relational
Tuple-at-a-Time Model
http://www.percona.com/software/percona-server
https://github.com/percona/percona-server
Percona
US
2006
Commercial, Open Source
MySQL
https://en.wikipedia.org/wiki/Percona_Server_for_MySQL