Lenovo DM120S, Installation And Cabling Manual, Page: 39 / 70

Chapter 7. SAS cabling rules
Disk shelves with IOM12 modules can be cabled in HA pair configurations by applying the SAS cabling rules:
configuration rules, controller slot numbering rules, shelf-to-shelf connection rules, and controller-to-stack
connection rules.
Note: The SAS cabling rules regarding controller slot numbering rules, shelf-to-shelf connection rules, and
controller-to-stack connection rules described in this guide are the same rules that apply to all SAS disk
shelves, whether they have IOM12, IOM6, or IOM3 modules. However, the information in this guide is
specific to the unique characteristics of disk shelves with IOM12 modules and their use in supported
configurations.The SAS cabling rules regarding configuration rules described in this guide are specific to disk
shelves with IOM12 modules.
The SAS cabling rules described in this guide balance SAS cabling between the on-board SAS ports and
host bus adapter SAS ports to provide highly available storage controller configurations and meet the
following goals:
• Provide a single, easily understood universal algorithm for all SAS products and configurations
• Yield the same physical cabling when generating the Bill of Materials (BOM), followed in the factory, and in
the field
• Are verifiable by configuration-checking software and tools
• Provide maximum possible resilience to maintain availability and minimize the reliance on controller
takeovers
You should avoid deviating from the rules; deviations might reduce reliability, universality, and commonality.
Configuration rules
Disk shelves with IOM12 modules are supported in specific types of HA pair configurations.
HA pair configurations must be cabled as multipath HA or quad-path HA configurations with the following
exceptions:
• DM3000x, DM5000x, or DM7000x HA pair configurations (with external disk shelves) can be cabled as
single-path HA configurations to support connectivity to an external SAS tape backup device.
• DM3000x, DM5000x, or DM7000x HA pair configurations do not support quad-path HA connectivity.
Controller slot numbering rules
For the purpose of applying cabling rules across all supported HA pairs configurations, a controller slot
numbering convention is used.
• For all HA pairs configurations, the following applies:
– A SAS HBA in a physical PCI slot is defined as occupying PCI slot 1, 2, 3, and so on regardless of the
slot's physical label on a controller. For example, if SAS HBAs occupied physical PCI slots 3, 5, and 7,
they would be designated as slots 1, 2, and 3 for the purpose of applying the SAS cabling rules.
– An onboard SAS HBA is defined as occupying PCI slot 0 just as it is labeled on a controller.
– Each port in each slot is defined just as it is labeled on a controller.
For example, slot 0 with two ports is referred to as 0a and 0b. Slot 1 with four ports is referred to as 1a, 1b,
1c, and 1d.
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