Administrator Guide

connectivity if one of the controllers fails. For optimal performance, the primary ports should be evenly distributed across both controllers.
When possible, front-end connections should be made to separate controller I/O cards to improve redundancy.
About Fault Domains and Ports
Fault domains group front‐end ports that are connected to the same transport media, such as a Fibre Channel fabric or Ethernet network.
Ports that belong to the same fault domain can fail over to each other because they have the same connectivity.
Front-end ports are categorized into fault domains that identify the allowed port movement when a controller reboots or a port fails.
Failure modes and port activity depend on whether the Storage Center is configured for Legacy mode, ALUA port mode, or Virtual port
mode.
Fault Domains for SCv2000 Series Storage Systems
The Storage Center handles all fault domain creation and modification on SCv2000 series.
Depending on the hardware configuration, the following fault domains are automatically created on SCv2000 series storage systems:
• For SCv2000 series storage systems with Fibre Channel HBAs, two fault domains are created for the Fibre Channel ports.
• For SCv2000 series storage systems with iSCSI HBAs, two fault domains are created for the iSCSI ports.
• For SCv2000 series storage systems with SAS HBAs, four fault domains are created for the SAS ports.
• Fault domains are automatically created for Flex/Embedded Ethernet ports.
NOTE: Additional front-end fault domains cannot be created on SCv2000 series storage systems . In addition, existing
fault domains cannot be modified or deleted on SCv2000 series storage systems .
Fault Domains for SCv3000 Series Storage Systems
The Storage Center handles all fault domain creation and modification on SCv3000 series storage systems.
Depending on the hardware configuration, the following fault domains are automatically created on SCv3000 series storage systems:
• For SCv3000 series storage systems with Fibre Channel HBAs, two fault domains are created for the Fibre Channel ports.
• For SCv3000 series storage systems with iSCSI HBAs, two fault domains are created for the iSCSI ports.
• For SCv3000 series storage systems with SAS HBAs, four fault domains are created for the SAS ports.
• For SCv3000 series storage systems with iSCSI mezzanine cards, two fault domains are created for the iSCSI ports.
• For SCv3000 series storage systems with iSCSI mezzanine cards and iSCSI HBAs, four fault domains are created for iSCSI ports
NOTE:
Additional front-end fault domains cannot be created on SCv3000 series storage systems. In addition, existing
fault domains cannot be modified or deleted on SCv3000 series storage systems.
Fault Domains for Front-End SAS Ports for SC4020 Storage Systems
Users can select the number of fault domains to create for front-end SAS ports on SC4020 Storage Systems.
Fault domain behavior on SC4020 Storage Systems:
• Storage Center generates the SAS fault domains by pairing un-used front-end SAS ports into fault domains. If all SAS front-end ports
are already included in fault domains, fault domains cannot be created.
• Storage Center uses one port from each controller.
• The paired ports have the same port number.
• Users can modify fault domain names and notes about the fault domain.
• Users can delete SAS fault domains.
• Users cannot add, move or remove ports within SAS fault domains.
Fault Domains in Virtual Port Mode
In virtual port mode, fault domains group front-end ports that are connected to the same Fibre Channel fabric or Ethernet network. All
ports in a fault domain are available for I/O. If a port fails, I/O is routed to another port in the fault domain.
The following requirements apply to fault domains in virtual port mode:
• Fault domains are created for each front-end Fibre Channel fabric or Ethernet network.
• A fault domain must contain a single type of transport media (FC or iSCSI, but not both).
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Storage Center Maintenance