A person familiar with the deal told The Associated Press on Friday that Ellis will be guaranteed at least $6 million. The person spoke on condition of anonymity because the team has not announced the signing.
The NFL Network first reported the agreement and its terms.
Ellis was slated to become an unrestricted free agent next week before the Raiders decided to keep the stout run-stopping defensive tackle.
Ellis was originally a fourth-round pick by Oakland in 2014. He has started 41 of the 60 games he has played in during four seasons with the Raiders.
The Raiders still need to find a pass-rushing threat inside. Ellis has only a half-sack in his career and has 3.5 quarterback pressures in 327 pass-rush snaps the past two seasons, according to SportRadar.
Information from The Associated Press was used in this report.