Intersite link planning

Specific intersite link requirements must be met when you are planning to use IP partnership for Policy-based replication or Policy-based HA.

If you use IP partnership, you must meet the following requirements:
  • On systems that support IP compression, IP partnerships can also support data compression. Both systems in the IP partnership must be running a software level that supports IP partnership data compression. Compression must also be functional on each system. For more information, see Creating IP partnership.
  • The amount of intersite heartbeat traffic is 1 megabit per second (Mbps) per link.
  • The minimum bandwidth requirement for the intersite link is 10 Mbps. However, this requirement scales up with the amount of host I/O that you choose to do. Figure 1 describes the scaling of host I/O.
    Figure 1. Scaling of host I/O
    Scaling of host I/O

    The equations that can describe the approximate minimum bandwidth that is required between two systems with < 5 ms round-trip time and errorless link follow.

    Increasing latency and errors results in a higher requirement for minimum bandwidth.

Figure 2 shows how the IBM Storage Virtualize solution maintains near line-speed performance by masking the latency of the line. Even as the line latency increases, the performance of the technology enables the line to continue to exceed that of a plain link. The throughput limit is the uncompressed data rate, which is measured as the remote node send data rates. The round-trip time (RTT) is measured as the IP link RTT (pinging between the two nodes on the same ports that are being used for replication). The throughput limit is based on the distance and the uncompressed data rate.

Figure 2. Product transfer rate comparison for systems built with IBM Storage Virtualize
IBM Storage Virtualize transfer rate comparison