SAS cabling rules
Disk shelves with IOM12 modules can be cabled in HA pair and single-controller configurations (for supported
platforms) by applying the SAS cabling rules: configuration rules, controller slot numbering rules, shelf-to-
shelf connection rules, controller-to-stack connection rules, and if applicable, mini-SAS HD SAS optical cable
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 and mini-SAS HD SAS optical cable 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 and single-controller
configurations.
• HA pair configurations must be cabled as multipath HA or quad-path HA configurations with the following
exceptions:
• HX2000 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.
• HX2000 series HA pair configurations do not support quad-path HA connectivity.
• Single-controller configurations must be cabled as multipath or quad-path configurations, with the
following exceptions:
• Single-controller configurations (with external disk shelves) can be cabled as single-path
configurations.
Because the internal storage uses single-path connectivity, ETERNUS AX/HX Series issues occasional
warnings that mixed paths are detected. To avoid these warnings, you can use single-path connectivity
to the external disk shelves. Additionally, you can use single-path connectivity when an external SAS
tape backup device is used.
• Single-controller configurations do not support quad-path connectivity.
Controller slot numbering rules
For the purpose of applying cabling rules across all supported HA pairs and single-controller configurations, a
controller slot numbering convention is used.
• For all HA pairs and single-controller 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.
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