HANA Multiple Host - What is it ?

SAP HANA MULTIPLE HOST
A multiple-host system is a system with more than one host, which can be configured as active worker hosts or idle standby hosts. The server software is based on a flexible architecture that enables a distributed installation. This means that load can be balanced between different hosts. The server software has to be installed in a shared file system. This file system has to be mounted by all hosts that are part of the system.

HANA Host Types 
When configuring a multiple-host system, the additional hosts must be defined as worker hosts or standby hosts (worker is default).

Worker machines process data.
Standby machines do not handle any processing and instead just wait to take over processes in the case of worker machine failure.