Mike Portnoy was in Dream Theater.
Michael Stephen `` Mike '' Portnoy ( born April 20 , 1967 ) is an American drummer primarily known as the former drummer , backing vocalist , and a co-founder of the progressive metal/rock band Dream Theater . He co-produced six Dream Theater albums with guitarist John Petrucci , starting from Metropolis Pt . Besides his work with Dream Theater , Portnoy is known for his many side projects and tribute bands . In September 2010 , Portnoy announced his departure from Dream Theater after 25 years .