Michael Stephen Portnoy (born April 20, 1967) is an American musician who is primarily known as the former drummer, backing vocalist, and co-founder of the progressive metal band Dream Theater. In September 2010, Portnoy announced his departure from Dream Theater after 25 years, with Mike Mangini taking his place as drummer of the band. Since his departure Portnoy has remained active, with a variety of bands and projects, including Adrenaline Mob, Transatlantic, Yellow Matter Custard, Flying Colors, The Winery Dogs, Liquid Tension Experiment, Metal Allegiance, Sons of Apollo, the Neal Morse Band and BPMD.

Source: Wikipedia (https://en.wikipedia.org/wiki/Mike_Portnoy)