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I/O Path Definitions for Redundant FCALs

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2-34 Compaq Parallel Database Cluster Model PDC/O5000 for Oracle8i and Windows 2000 Administrator Guide If any component along an active path fails, Secure Path detects the failure and automatically transfers all I/O activity to the defined backup path. I/O Path Definitions for Redundant FC-ALs In a redundant FC-AL, devices are accessed by the operating system using conventional SCSI addressing terminology. An I/O path consists of the complete physical interconnections from a given host (node) to a specific RAID storageset in a shared storage subsystem. Each path is identified by a unique 4-bit value that contains the port number (host adapter), bus number, and the unit name's target ID and LUN. Each unit name's target ID and LUN values use the format "Dxxyy," where 'xx' is the target number (0-15) and 'yy' is the LUN (0-7). A target number of 0 is always dropped from the unit number designation (for example, the unit number D0 is understood to be LUN0 on target 0). A host (node) uses the unit name to specify the source or target for every I/O request it sends to an array controller. The unit name can identify a single physical disk drive unit or a storageset that contains several disk drives. The port number (HBA) is assigned by the Windows 2000 Advanced Server operating system. Except for the LUN, the rest of the SCSI address is created within the host adapter miniport driver and is derived from the Arbitrated Loop Physical Address (ALPA) assigned to each of the four array controller ports in a shared storage subsystem. The miniport driver uses a fixed mapping scheme to translate ALPA assignments to SCSI bus and target ID values. The LUN number is derived from the unit number that has been assigned to the storageset using the StorageWorks Command Console (SWCC) or Command Line Interface (CLI) commands. Each node must also have a unique ALPA. Each storageset created in a MA8000/EMA12000 Storage Subsystem must have a unique unit name. Since these storage subsystems present an identical address space from both of their two array controllers, the only bit of address information that will be different across the I/O paths from a given node to a specific storageset is the port (HBA) number.

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2-34
Compaq Parallel Database Cluster Model PDC/O5000 for Oracle8i and Windows 2000 Administrator Guide
If any component along an active path fails, Secure Path detects the failure and
automatically transfers all I/O activity to the defined backup path.
I/O Path Definitions for Redundant FC-ALs
In a redundant FC-AL, devices are accessed by the operating system using
conventional SCSI addressing terminology. An I/O path consists of the
complete physical interconnections from a given host (node) to a specific
RAID storageset in a shared storage subsystem. Each path is identified by a
unique 4-bit value that contains the port number (host adapter), bus number,
and the unit name
’
s target ID and LUN. Each unit name
’
s target ID and LUN
values use the format
“
D
xxyy
,
”
where
‘
xx
’
is the target number (0-15) and
‘
yy
’
is the LUN (0-7). A target number of 0 is always dropped from the unit
number designation (for example, the unit number D0 is understood to be
LUN0 on target 0). A host (node) uses the unit name to specify the source or
target for every I/O request it sends to an array controller. The unit name can
identify a single physical disk drive unit or a storageset that contains several
disk drives.
The port number (HBA) is assigned by the Windows 2000 Advanced Server
operating system. Except for the LUN, the rest of the SCSI address is created
within the host adapter miniport driver and is derived from the Arbitrated
Loop Physical Address (ALPA) assigned to each of the four array controller
ports in a shared storage subsystem. The miniport driver uses a fixed mapping
scheme to translate ALPA assignments to SCSI bus and target ID values. The
LUN number is derived from the unit number that has been assigned to the
storageset using the StorageWorks Command Console (SWCC) or Command
Line Interface (CLI) commands. Each node must also have a unique ALPA.
Each storageset created in a MA8000/EMA12000 Storage Subsystem must
have a unique unit name. Since these storage subsystems present an identical
address space from both of their two array controllers, the only bit of address
information that will be different across the I/O paths from a given node to a
specific storageset is the port (HBA) number.