Controller-To-Stack Connection Rules - Fujitsu ETERNUS AX Series Installation And Cabling Manual

• Double-wide shelf-to-shelf connectivity requires two cable connections between disk shelves in each
domain—domain A (IOM A) and domain B (IOM B).
The first cable connection is cabled as standard shelf-to-shelf connectivity (using IOM ports 3 and 1); the
second cable connection is cabled as double-wide shelf-to-shelf connectivity (using IOM ports 4 and 2).
From the logical first shelf to the logical last shelf in a stack, you connect IOM port 3 to the next shelf's IOM
port 1 in domain A and then domain B. From the logical first shelf to the logical last shelf in a stack, you
connect IOM port 4 to the next shelf's IOM port 2 in domain A and then domain B. (IOM ports cabled as
double-wide connectivity are shown with blue.)

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 HX2000 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 ETERNUS AX/HX Series (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 HX2000 configurations)
• A and C ports are always the primary paths to a stack.
• A and C ports always connect to the logical first disk shelf in a stack.
• A and C ports always connect to disk shelf IOM ports 1 and 2.
IOM port 2 is only used for quad-path HA and quad-path configurations.
• Controller 1 A and C ports always connect to IOM A (domain A).
• Controller 2 A and C ports always connect to IOM B (domain B).
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.
| SAS cabling rules |
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