Common Requirements

This section describes the requirements that are common to both topologies:

• General Requirements

• HADB Nodes and Machines

• Load Balancer Configuration

General Requirements

Both topologies must meet the following general requirements:

• Machines that host HADB nodes must be in pairs. That is, there must be an even number of them.

• Each data redundancy unit (DRU) must have the same number of machines. Create the HADB database in such a way that the mirrored (paired) nodes are on a different DRU than the primary nodes.

• Each machine that hosts HADB nodes must have local disk storage, used to store all persisted information in the HADB.

• Machines that host the HADB nodes must run the same operating system. It is best to use identical or nearly identical machines, in terms of configuration and performance.

• For HTTP and SFSB session information to be persisted to the HADB, the Enterprise Server instances must be in a cluster and satisfy all related requirements.

• Machines hosting the Enterprise Server instances must be as identical as possible, in terms of configuration and performance. This is because the load balancer plug-in uses a round-robin policy for load balancing, and if machines of different classes host instances, then the load will not be balanced in the most optimum way across these machines.

• Preferably have a separate uninterruptible power supply (UPS) for each DRU.

HADB Nodes and Machines

Each DRU contains a complete copy of the data in HADB and can continue servicing requests if the other DRU becomes unavailable. However, if a node in one DRU and its mirror in another DRU fail at the same time, some portion of data is lost. For this reason, it is important that the system is not set up so that both DRUs can be affected by a single failure such as a power failure or disk failure.

Each DRU must run on a completely independent, redundant system.

Follow these guidelines when setting up the HADB nodes and machines:

• To increase capacity and throughput, add nodes in pairs with one node for each DRU.

• Set up each DRU with a number of spare nodes equal to the number of nodes running on each machine. This is because if each machine in the configuration runs n data nodes, the failure of a single machine brings down n nodes.

• Run the same number of HADB nodes on all machines to balance load as evenly as possible.

Do not run nodes from different DRUs on the same machine. If you must run nodes from different DRUs on the same machine, ensure that the machine can handle any single point of failure (for failures related to disk, memory, CPU, power, operating system crashes, and so on).

Load Balancer Configuration

Both the topologies have Enterprise Server instances in a cluster. These instances persist session information to the HADB. Configure the load balancer to include configuration information for all the Enterprise Server instances in the cluster.