Thanks all for the feedback. It was a nice idea and it *almost* works, but it seems like we just can't drop segmented mode. And the automatic transition schemes I showed don't make much sense without that goal.
What I'm hearing is that something simple like this might be more acceptable: * initdb --rel-segsize (cf --wal-segsize), default unchanged * pg_upgrade would convert if source and target don't match I would probably also leave out those Windows file API changes, too. --rel-segsize would simply refuse larger sizes until someone does the work on that platform, to keep the initial proposal small. I would probably leave the experimental copy_on_write() ideas out too, for separate discussion in a separate proposal.
