Renov: 17' is WAY too much to span. I would highly recomend adding an intermediary post (or 2) equally spaced between the ends.
Huh? Just beef up your beams and you can span 17', no problem. Usually, if you're spanning a roof beam over a back deck, the middle of that span will fall right near the sliding glass door. You don't want a post right near the door.
That being said, don't even think about a single 2x to span it, I don't care if it's a 2x12, it ain't enough. For a 17' span w/ 2x6s spaced 12" o.c., I'd go with a 4x10 beam sitting on notched 6x6 posts.
Drop your 6x6s 3' into the ground with the bottom end sitting on packed gravel.
Pour a 16" dia. x 4' tall concrete ring (w/ rebar) around the posts so concrete is 1' above grade.
Slope the top of the concrete so water drips away from the post.
Simpson's got 4x6 post caps that you can get powdercoated, or use a metal guy in town.
To cut down on sway for a top heavy, 4 post structure, run beams from front post to back post, perpendicular to your support beams.
Then you can run knee bracing in 3 planes - post to support beam, post to perp. beam and a horizontal knee brace from perp. beam to support beam.
Do that on all four corners and you've got a solid structure (esp. since it's only 8' deep.)
ChrWright, nice looking work, man! Got any close-up pics? Is that a reverse shed-style rain roof over the front porch? How do you support the back end of the roof (over the house roof)?
Here's one I did similar in style to that. Patio roof hangs over house roof by 18" or so so rain is collected in existing gutter system. I cut 6"x6" blocks, buttered that bottoms w/ a crapload of black tar-like roof caulk, positioned them every 4' over a rafter and ran a LedgerLock through into the rafter. I set a 4x4 beam on those blocks, screwed into place and set my rafter tails on that.
Mac