The data tier failover cluster provides high availability and fault tolerance.
Two data tier hosts, each managed by a Windows-based failover cluster service
At least one fault-tolerant storage device, which provides the shared cluster storage for database files and transaction logs
Each data tier host is a redundant node in the failover cluster—one active, and one standby (or passive). Host system performance is more critical for the data tier servers, because each host must assume the entire load imposed by the SAP Mobile Server cluster.
All data tier server software must be installed on a local drive, on each data tier host. The data tier software cannot be installed on shared cluster storage, or on any storage resource that can be managed independent of the data tier host.
All data tier database files and transaction logs must be located on a shared-cluster storage device, such as a SAN device that is assigned the appropriate RAID level.
Each data tier host must be physically connected, by a host bus adapter, to the shared cluster storage device. Each volume that houses a database file system must be accessed as a local disk, on each data tier host.
All data tier services must be configured as cluster resources, managed in the context of a common cluster instance.
To a SAP Mobile Server, data tier hosts in a failover cluster appear to be a single, logical data tier entity.