Duchene made it 2-0 at 18:30 with a shot through traffic from the blue line that deflected off the left post.
Luff increased the lead to 3-0 at 2:43 of the second period when Josi's point shot deflected off him short side.
"I think, regardless of the score, at 3-0 I thought we're actually playing a pretty competitive game," Sharks coach Bob Boughner said. "We were playing pretty hard. We only gave up two chances in the first period and we only generated one, so it was pretty even in the first period regardless of the shot clock. … Once it [became] 4-0, we got away from our game and you start pressing and things start going in, and that's a snowball you can't stop."
Luff scored his second of the period to make it 4-0 at 19:30. Stalock saved two shots from point-blank range, but after Tomasino's attempt was blocked by Nicolas Meloche in the crease, Luff got the loose puck and shot into an open net.
"That fourth goal seemed to break us and it went from there," San Jose forward Nick Bonino said.
Duchene pushed it to 5-0 at 4:43 of the third period before McCarron redirected a centering pass to chase Stalock and make it 6-0 at 6:07.
Yakov Trenin made it 7-0 at 11:13 following a turnover by Marc-Edouard Vlasic, and Mikael Granlund scored a power-play goal at 13:06 for the 8-0 final.
"This is a teachable tape for sure," Boughner said. "The good part is, we're going back to work tomorrow. We've got to put that one behind us and play an [Anaheim Ducks] team that is desperate."
NOTES: The Predators scored at least eight goals in game for the eighth time, the first since Dec. 17, 2019 (8-3 at the New York Islanders). Nashville has scored nine goals three times. ... It was Josi's second NHL game with four assists. He had five on Feb. 27, 2018 against the Winnipeg Jets.