Adaptec 1966600 User Guide - Page 85

Installing the DuraStor Storage Subsystem Hubs Disabled (Single-Port Hosts and One Switch) In Figure 3-46, two single-ported hosts connected to the DuraStor 7220SS storage subsystem's two controllers via a single switch. In this case, there would be an advantage to configuring the controllers in active-active dual-port mode, because of increased connectivity. However, the host driver software would need to handle the fact that each LUN would appear twice in the SAN fabric, and that one image of the LUNs would disappear if one controller failed. Depending on the host software being used, it may be more desirable to run in active-active single-port mode, since a controller failover would be transparent to the hosts (as far as the number of LUN images and the port WWNs attached to the LUNs). The advantages of using a switch is that the two hosts each have a direct path to a controller port and don't have to compete for access on the same loop. DuraStor FC RAID Appliance Host 1 Host Link 1 FC HBA Host 2 P2 Switch P1 P3 P4 FC HBA Host Link 2 LUN 2 CH0 FC2 Passive CH1 FC1 LUN 2 Active CH2 Controller 2 CH3 LUN 1 FC1 Active FC2 LUN 1 Passive Controller 1 CH0 T CH1 T CH2 T CH3 T Figure 3-46 Active-Active Single-Port Hubs Disabled CH0 Up to 12 Disk Drives CH1 Up to 12 Disk Drives CH2 Up to 12 Disk Drives CH3 Up to 12 Disk Drives 3-51