What is Super Seed mode? When should I enable it?
Super Seeding is a special optimised seeding mode. It allows seeders who are the only seed in the swarm to solely seed pieces that are found nowhere else in the swarm. It works something like this: the superseeding client pretends not to be a seed, but pretends to be a peer with an incomplete file. Then the client shares each piece with one peer only. And that peer can then share that piece with the swarm. This allows the superseeding client to maximise the efficiency of the upload by only sharing those pieces nobody else has. And because of some other things about the behaviour of superseeding, this function does not work at all well in swarms with one peer and one seed only. So it is only good when the seeder is the only seed (usually the original uploader), and there are more than two peers. For more information please see Seeding Rules.
Only use this mode when you are the first and only seeder = the original uploader of the file.
When activated, additional information is available in the details view, right-click, "Choose the columns to display".
Some additional info from Gouss:
Azureus superseeding mode is for initial seeding only (or 1 seed only).
It goes through pieces from start to end.
It announces one piece at a time to peers and prioritizes big uploaders.
A piece is taken off the list of pieces to send if:
1. it's been sent once,
2. it's already available in the swarm.
Once each piece has been sent once (or is available once), Azureus switches back to normal mode. (It has to disconnect because it announced different bitfields to each client...)
This superseeding mode is automatic, but you can choose to use it or not.
If the swarm needs superseeding, it'll kick in, and back out if not.
Normal seeding mode doesn't include a "rarest first" on the server side.
As pointed out, if a peer quits, the pieces sent to him won't be sent again.
Q: When looking at the Details, the extra Super-Seed Mode columns (Piece & Time to resend Piece) show None and blank. I have Super Seed checked in the Configuration Seeding options, but does this mean that I'm not Super Seeding even though I'm the only seed in the swarm?
A: Correct, you are not Super Seeding. This is probably because you didn't restart Azureus after you enabled Super Seeding (and thus the change did not take effect).
Read the Azureus FAQ