Communications requirements

Depending on how you plan to use independent disk pools, you must satisfy the following communications requirements:

Single-system environment

There are no communications requirements.

Multisystem clustered environment

Switchable independent disk pools and independent disk pools that are geographically mirrored are configured within an iSeries™ cluster. The communication requirements include the following:

For switchable independent disk pools, at least one TCP/IP communications interface between the servers in the cluster. For redundancy, it is recommended that there be at least two separate interfaces between the servers.
For geographic mirroring, the following are recommended:
- Up to a maximum of four unique TCP/IP addresses, used exclusively for geographic mirroring. Geographic mirroring can generate heavy communications traffic. If geographic mirroring shares the same IP connection with another application, for example clustering, then geographic mirroring might be suspended which results in synchronization. Likewise, clustering response might be unacceptable which results in partitioned nodes.
- Throughput for each data port connection should match, meaning that the speed and connection type should be the same for all connections between server pairs. If throughput is different, performance will be gated by the slowest connection.
Consider configuring a virtual private network for TCP/IP connections for the following advantages:
- Security of data transmission by encrypting the data
- Increased reliability of data transmission by sending greater redundancy

Connections from the production system

Geographic mirroring will establish connections from the production system to each of the data port TCP/IP addresses on the mirror copy. TCP can choose to connect from any available TCP/IP address on the production system according to the TCP routing table. The TCP address used is not limited to the addresses configured for geographic mirroring on the production system. TCP may select the same TCP/IP address on the production system to connect to each TCP/IP address on the mirror copy. To control which TCP/IP address(es) on the production system are used to connect to each address on the mirror copy, TCP/IP routes can be created. This is useful to control which addresses on the production system will be chosen for geographic mirroring. It can also eliminate a single point of failure and potential bottleneck caused when all connections are created from the same TCP/IP address.