Fujitsu ETERNUS AX Series Installation And Cabling Manual page 37

Port pair connection rules (for non HX2000 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.
• Port pairs consist of a controller A or C SAS port and a controller B or D SAS port.
A and C SAS ports connect to the logical first shelf in a stack. B and D SAS ports connect to the logical last
shelf in a stack.
• Port pairs use all SAS ports on each controller in your system.
You increase system resiliency by incorporating all SAS ports (on an HBA in a physical PCI slot [slot 1-N]
and on board the controller [slot 0]) into port pairs. Do not exclude any SAS ports.
• Port pairs are identified and organized as follows:
1. List A ports and then C ports in sequence of slots (0,1, 2, 3, and so on).
For example: 1a, 2a, 3a, 1c, 2c, 3c
2. List B ports and then D ports in sequence of slots (0,1, 2, 3, and so on).
For example: 1b, 2b, 3b, 1d, 2d, 3d
3. Rewrite the D and B port list so that the first port in the list is moved to the end of the list.
For example:
Offsetting the order of the slots by one balances port pairs across multiple slots (physical PCI slots and
on board slots) when more than one slot of SAS ports is available; therefore, preventing a stack from
being cabled to a single SAS HBA.
4. Pair the A and C ports (listed in step 1) to the D and B ports (listed in step 2) in the order that they are
listed.
For example: 1a/2b, 2a/3b, 3a/1d,1c/2d, 2c/3d, 3c/1b.
Note: For an HA pair, the list of port pairs you identify for the first controller is also applicable to the
second controller.
• When cabling your system, you can use port pairs in the order in which you identified them or you can skip
port pairs:
• Use port pairs in the order in which you identified (listed) them when all port pairs are needed to cable
the stacks in your system.
For example, if you identified six port pairs for your system and you have six stacks to cable as
multipath, you cable the port pairs in the order in which you listed them:
1a/2b, 2a/3b, 3a/1d,1c/2d, 2c/3d, 3c/1b
• Skip port pairs (use every other port pair) when not all port pairs are needed to cable the stacks in your
system.
For example, if you identified six port pairs for your system and you have three stacks to cable as
multipath, you cable every other port pair in your list:
Note: When you have more port pairs than you need to cable the stacks in your system, the best
practice is to skip port pairs to optimize the SAS ports on your system. By optimizing SAS ports, you
optimize your system's performance.
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
| SAS cabling rules |
on page 40
on page 44
37