Controller-to-stack connection rules

You can correctly cable the SAS connections from each controller to each stack in an HA pair or in a single-controller configuration by understanding that SAS disk shelves use software-based disk ownership, how controller ports A/C and B/D are connected to stacks, how controller ports A/C and B/D are organized into port pairs, and how FAS2600 series ports 0b and 0a are connected to stacks.

SAS disk shelf software-based disk ownership rule

SAS disk shelves use software-based disk ownership (not hardware-based disk ownership). This means that disk drive ownership is stored on the disk drive rather than it being determined by the topology of the storage system's physical connections (as it is for hardware-based disk ownership). Specifically, disk drive ownership is assigned by ONTAP (automatically or by CLI commands), not by how you cable the controller-to-stack connections.

SAS disk shelves should never be cabled using the hardware-based disk ownership scheme.

Controller A and C port connection rules (for non FAS2600 series configurations)

The following illustration highlights how controller ports A and C connect in a multipath HA configuration with one quad-port HBA and two stacks of disk shelves. Connections to stack 1 are shown in blue. Connections to stack 2 are shown in orange.



Controller B and D port connection rules (for non FAS2600 series configurations)

The following illustration highlights how controller ports B and D connect in a multipath HA configuration with one quad-port HBA and two stacks of disk shelves. Connections to stack 1 are shown in blue. Connections to stack 2 are shown in orange.



Port pair connection rules (for non FAS2600 series configurations)

Controller SAS ports A, B, C, and D are organized into port pairs using a method that leverages all of the SAS ports for system resiliency and consistency when cabling controller-to-stack connections in HA pair and single-controller configurations.

Controller-to-stack cabling worksheets are convenient tools for identifying and organizing port pairs so that you can cable the controller-to-stack connections for your HA pair or single-controller configuration.

Controller-to-stack cabling worksheet template for multipathed connectivity

Controller-to-stack cabling worksheet template for quad-pathed connectivity

FAS2600 series controller 0b and 0a port connection rules to external disk shelves

The FAS2600 series has a unique set of connection rules because each controller must maintain same domain connectivity between the internal storage (port 0b) and the stack. This means that when a controller is located in slot A of the chassis (controller 1) it is in domain A (IOM A) and therefore port 0b must connect to IOM A in the stack. When a controller is located in slot B of the chassis (controller 2) it is in domain B (IOM B) and therefore port 0b must connect to IOM B in the stack.
Note: If you do not connect the 0b port to the correct domain (cross-connect domains), you expose your system to resiliency issues that prevent you from performing nondisruptive procedures safely.
  • Controller 0b port (internal storage port):
    • Controller 1 0b port always connects to IOM A (domain A).
    • Controller 2 0b port always connects to IOM B (domain B).
    • Port 0b is always the primary path.
    • Port 0b always connects to the logical last disk shelf in a stack.
    • Port 0b always connect to disk shelf IOM port 3.
  • Controller 0a port (internal HBA port):
    • Controller 1 0a port always connects to IOM B (domain B).
    • Controller 2 0a port always connects to IOM A (domain A).
    • Port 0a is always the secondary path.
    • Port 0a always connects to the logical first disk shelf in a stack.
    • Port 0a always connect to disk shelf IOM port 1.

The following illustration highlights internal storage port (0b) domain connectivity for a FAS2600 series multipath HA configuration: