San Jose goaltender Martin Jones made 45 saves, a career high in the Stanley Cup Playoffs, and Joonas Donskoi and Logan Couture each had a goal and two assists.
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The Sharks, who set their playoff record for goals in a game, took control in the second period when Donskoi, Marcus Sorensen, Eric Fehr and Tomas Hertl scored four straight goals for a 5-1 lead.
San Jose is 4-1 all time in playoff series when it has taken a 3-0 lead, its only loss coming in the 2014 first round against the Los Angeles Kings.
"We understand there's a lot of work to do," Sharks captain Joe Pavelski said. "Eliminating teams is always tough. That's kind of where our mindset shifts, I think."
The Ducks are 0-3 in series when they have lost the first three games.
"We know what happened," Anaheim defenseman Josh Manson said. "It's embarrassing. It's not good enough. Now it's do or die, so if you dwell on a game like this, it gets you nowhere."
John Gibson allowed five goals on 24 shots and was replaced for the third period by Ryan Miller, who made nine saves.
Jones made 19 saves in the second period when the Sharks pulled away.