Chapter 3: Subsystem Connection
3-5
3.2.4 Drive-side Connection
The drive-side connection is made through redundant data paths on the
back-end PCB that are compatible with the dual-ported connectivity feature
of SAS drives. Disk drives are connected through separated SAS domains.
And these domains are separately managed by different RAID controllers.
I/Os are dynamically distributed through these separate domains; and, in the
event of single RAID controller failure, the surviving controller can access
disk drives through both domains.
3.2.5 Internal
Connections
The internal connections described here only applied in the GHDX2-1430F-
16F4D redundant controller subsystem. The two (2) controllers are
connected to each other internally through the backplane board. This also
enables the two (2) controllers to synchronize their caches and dynamically
distribute the workload according to firmware load-balancing algorithms.
If you prefer cost-effective SATA drives in the subsystem, MUX boards are
necessary for directing accesses from different RAID controllers. MUX
boards come as default equipment in the dual-controller model.
3.2.6 Unique
Identifier
The unique identifier is a 16-bit hexadecimal number that is used to generate
Fibre Channel port names and node names. By factory defaults, each RAID
controller is assigned with a separate hexadecimal number and the firmware
then determines which unique identifier to use. It is usually not necessary to
change the default identifier. To see how to use the front panel LCD screen
or the terminal emulation program to enter the unique identifier, please refer
to the
Fibre-to-SAS RAID Subsystem Operation Manual
.
3.2.7 ID/LUN
Mapping
I/O load distribution between the RAID controllers is determined by the
host ID/LUN mapping. Different logical groups of drives can be mapped to
the LUN numbers under a host ID. For access through different host links,
e.g., in a multiple data links configuration, a logical drive configuration can
be associated with different ID/LUN combinations on different host
channels. In this case, file locking or multi-pathing control is necessary.
ID/LUN mapping procedures are described fully in the Fibre-to-SAS
firmware Operation Manual.