Hi,
please refer to the right version of the documentation. You initially posted the URL to a 5.6.1 documentation, and clustering has totally changed in 6.0. When you start with AEM 6.0 in a fresh installation, you will use Oak (aka CRX 3) and TarMK. TarMK does not support active-active clustering at the moment. If you want to have an active-active cluster, you need to use MongoDB.
And anyways: Before you start to use clustering, please upgrade your instance(s) to the most recent servicepack (sp2 at the moment). I also encourage you to get in contact with AEM support (aka Daycare) regarding this, plus also any other recommended hotfix.
kind regards,
Jörg