If you have problems when downloading large results sets from reDash it may be you are running against the default 30 seconds timeout in gunicorn. To solve this you can edit your:
/opt/redash/supervisord/supervisord.conf
and change:
[program:redash_server]
command=/opt/redash/current/bin/run gunicorn -b 127.0.0.1:5000 --name redash -w 4 redash.wsgi:app