basic aegir migration steps

1. SETUP NEW SERVER
install aegir, make a platform

2. CREATE ALIASES & SITE NODES FOR EACH SITE
drush provision-save @mysite.com --context_type=site --platform=@platform_mynewplatform --uri=mysite.com --client=admin --db_server=@server_mydb.server.com
drush hosting-import @mysite.com
drush @mysite.com provison-enable

3. BACKUP SITES ON THE OLD SERVER
cd /var/aegir/platforms/my-old-platform
drush provision-backup mysite.com

4. COPY BACKUPS
rsync backups newserver:oldserverbackups

5. DEPLOY FROM BACKUPS ON NEW SERVER
drush @mysite.com provision-deploy ~/old-server-backups/mysite.com-20111207.133251.tar.gz

repeat steps 3, 4, 5 as needed