HP P4000 9.0 HP StorageWorks P4000 Multi-Site HA/DR Solution Pack User Guide - Page 14

Best practices for implementing the Multi-Site SAN network • Adequate bandwidth-Plan for 50 MB/sec of bandwidth for each storage system in each site. For instance, if each site contains five storage systems, then you need 250 MB/sec throughput. In this case, that translates into two Gigabit Ethernet links, or more. • Low round-trip latency-In order to not impact disk I/O to the application server, the round-trip latency between the sites must be no more than 2 ms. • Redundant links-Have multiple physical connections (media) between the sites for redundancy. The network should be configured so that a link failure does not cause the Multi-Site SAN to go offline. • Assign servers to sites-Avoid high-latency connections by assigning application servers to the site where the server is located. Application servers assigned to a site connect only to storage systems in the same site as follows: • Without MPIO-With servers set up in the CMC with the load balancing option, the system sets up the iSCSI session only to storage systems assigned to the same site. • With MPIO and the HP DSM-The system sets up iSCSI sessions only to storage systems assigned to the same site. • With MPIO and the Microsoft DSM-With servers set up in the CMC with the load balancing option, the system sets up the iSCSI session only to storage systems assigned to the same site. • Use the Failover Manager-Unless you have storage systems in three physical sites, use a Failover Manager. Put the Failover Manager in the third site (physical or logical) located on a network that is isolated from the other sites and has a different power connection. Common Multi-Site SAN network designs Based on the Multi-Site SAN configuration, there are many network designs that can be implemented that solve the redundancy, high availability, and performance requirements for the Multi-Site SAN. A few commonly used designs are: • Dual redundant links between the sites • Full-mesh triangular (three) redundant links between sites • Hub and spoke central network core with redundant links out to each site • Combination full-mesh core network with triangular (three) links between sites Balancing the requirements for high availability during certain types of failures in the Multi-Site SAN and the budget associated with the network infrastructure typically dictates the network architecture a customer will choose to implement. Obviously, the most redundant network typically will cost the most to implement. However, not implementing redundancy in the Multi-Site SAN network significantly curtails the benefits of the Multi-Site SAN software. Table 4 on page 14 shows the common Multi-Site network configurations and the types of failures against which they provide protection. Table 4 Common Multi-Site network configurations and failure protection of each Network topology Dual redundant links between sites Full-mesh triangular links between sites Site failure protec- Network failure pro- Storage system tion tection failure protection Yes, with manual intervention Yes Yes Yes Yes Yes 14 Designing a Multi-Site SAN