rsync

Using temporary files to store and transfer sql-dump. It is recommended that you specify --source-dump and --target-dump options on the command line, or set '%dump' or '%dump-dir' in the path-aliases section of your site alias records. This facilitates fast file transfer via rsync.

What exactly does that mean? Is some random location i make up really better than the temporary directory? Or should i be giving it some specific directory, on different serves or something? Guidance please.

Failure

in drushrc.php

Believe it or not, this is the function you want:

core-rsync (rsync) Rsync the Drupal tree to/from another server using ssh.

For example:

drush rsync @example.stage:%files @example.local:%files

Can't do remote to remote though.