Dot Hill Systems II 200 FC service manual Remember these important rules

Note – Multipathing for FC, SATA, and SATA SE arrays is provided by SANpath software.

Remember these important rules:

■A single logical drive can be mapped to only one controller, either the primary controller or the secondary controller.

■In a point-to-point configuration, only one host ID per channel is allowed. The host ID can be assigned to the primary controller and be a PID, or it can be assigned to the secondary controller and be a SID.

■If you have two switches and set up multipathing (to keep all logical drive connections operational for any switch failure or the removal of any I/O controller module), ensure that each logical drive is mapped to two ports, one on each I/O controller module, and on two channels. The cables from the two ports mapped to each logical drive must be cabled to two separate switches. See Figure 5-1and Figure 5-2for examples of this configuration.

The following figures (Figure 5-1and Figure 5-2) show the channel numbers (0, 1, 4, and 5) of each host port and the host ID for each channel. N/A means that the port does not have a second ID assignment. The primary controller is the top I/O controller module, and the secondary controller is the bottom I/O controller module.

The dashed lines between two ports indicate a port bypass circuit that functions as a mini-hub. The port bypass circuit on each channel connects the upper and lower ports on the same channel and provides access to both controllers at the same time. If there are two host connections to the upper and lower ports on Channel 0, and one host connection is removed, the other host connection remains operational. Therefore, if you have a redundant multipathing configuration in which you have two host connections to each logical drive and one connection fails, the remaining path maintains a connection to the logical drive.

In Figure 5-1and Figure 5-2,with multipathing software to reroute the data paths, each logical drive remains fully operational when the following conditions occur:

■One switch fails or is disconnected, and the logical drive is routed to the second switch. For example, if switch 0 fails, switch 1 automatically accesses logical drive 0 through the cabling to the lower port on PID 41.

■One I/O controller module fails, and all the host IDs for that controller are reassigned (moved) to the second 1/O controller module. For example, if the upper I/O controller module is removed, host IDs 40 and 41 are automatically moved to the lower module and are managed by the second controller.

■An I/O controller module fails or one cable is removed from an I/O controller module, and all I/O traffic to the disconnected channel is rerouted through the second port/host LUN assigned to the logical drive. For example, if you remove the cable to channel 4, the data path for logical drive 1 switches to the port on channel 5.

5-6SANnet II 200 FC, SATA, and SATA SE Array Installation, Operation, and Service Manual • March 2005