NonStop NS14000 Series Planning Guide (H06.13+)

Configuration Restrictions for Fibre Channel Devices
To avoid creating configurations that are not fault-tolerant or do not promote high availability,
these restrictions apply and are invoked by Subsystem Control Facility (SCF):
• Primary and mirror disk drives in FCDMs cannot connect to the same Fibre Channel loop. Loss
of the Fibre Channel loop makes both the primary volume and the mirrored volume inaccessible.
This configuration inhibits fault tolerance.
• Disk drives in different FCDMs within a daisy-chain connect to the same Fibre Channel loop.
• The primary path and backup Fibre Channel communication links to a disk drive should not
connect to Fibre Channel ports in the same VIO enclosure. Loss of one Fibre Channel port can
make multiple disk drives inaccessible on a single Fibre Channel communications path. This
configuration is allowed, but only if you override an SCF warning message.
• The mirror path and mirror backup Fibre Channel communication links to a disk drive should
not connect to Fibre Channel ports in the same VIO enclosure. Loss of one Fibre Channel port
can make multiple disk drives inaccessible on a single Fibre Channel communications path.
This configuration is allowed, but only if you override an SCF warning message.
Recommendations for Fibre Channel Device Configurations
Recommendations for Fibre Channel Device Configuration
Different device types should be on different Fibre channel loops. For example, do not put disk
and tape devices on the same Fibre Channel loop.
These recommendations apply to VIO Fibre Channel ports and FCDM configurations:
• Primary FCDM connects to the VIO Fibre Channel port 1.
• Mirror FCDM connects to the VIO Fibre Channel port 2.
• FC-AL port A1 is the incoming port from a Fibre Channel port on the VIO enclosure or from
another FCDM.
• FC-AL port A2 is the outbound port to another FCDM.
• FC-AL port B2 is the incoming port from a Fibre Channel port on the VIO enclosure or from a
FCDM.
• FC-AL port B1 is the outbound port to another FCDM.
• In a daisy-chain configuration, the ID expander harness determines the enclosure number.
Enclosure 1 is always at the bottom of the chain.
• Fibre Channel ports are located in slot 1of a VIO enclosure.
• Ethernet ports are located in slots 6b, 6a/7a, and 7b of a VIO enclosure.
• The group number for a VIO enclosure is 100.
• With primary and mirror FCDMs in the same cabinet, the primary FCDM resides in a lower
U than the mirror FCDM.
• Fibre Channel disk drives are configured with dual paths.
• Where possible, Fibre Channel ports and FCDMs are configured with four Fibre Channel
ports and four FCDMs for maximum fault tolerance. If Fibre Channel ports are not in groups
of four, the remaining Fibre Channel ports and FCDMs can be configured in other fault-tolerant
configurations, such as with two Fibre Channel ports and two FCDMs or four Fibre Channel
ports and three FCDMs.
Fibre Channel Devices 75