Since many years, the SAP on IBM i Reference Architecture document is available to provide an overview over sample configurations and best practices when running SAP software on IBM i. It is the starting point for planning a complete new installation or enhancing existing systems for certain use cases, such as implementing high availability or adding specific solution components.
The document has recently been updated to cover the latest technology for hardware, high availability options and application software. In addition, many links to further reading have been updated or added. The 2017 version of the SAP on IBM i Architecture can be downloaded here: https://www.sap.com/documents/2015/08/fc338289-5b7c-0010-82c7-eda71af511fa.html.