Installation guide

External RAID Controller Operation Overview
4-56 GAM Client v3.00 and WSAM User’s Manual
External RAID Controller Operation Overview
External RAID Controllers use their host ports to connect to one or more
Host Bus Adapters in one or more host computer systems.
Depending on the model and configuration of the controller, there may be
from one to four host ports. Each configured logical drive consumes a
particular bus-target ID-LUN on the host system. Multiple sets of disk drives
are connected to the controller via its drive channels. There may be as many
as six drive channels, depending on the controller model and configuration.
In duplex, or Active/Active mode, two identical External RAID Controllers
are connected to the same hosts via their host ports, to the same drives via
their drive channels, and to each other via a special hardware link for
heartbeat sensing. This forms a redundant controller system. The two
controllers work together handling data traffic and mirror their write data in
each other’s cache memory. If one of the controllers fails or otherwise
becomes non-operational, the surviving controller takes over its
responsibilities with no loss of data.
☛ Note
This section presents only a brief introduction to
External RAID Controller operation. For additional
details, consult the hardware installation guide for the
particular controller of interest.
Two schemes for LUN Mapping exist depending on the version of the
External RAID Controller firmware in use:
• External Firmware 5.x and below uses a basic LUN Mapping system.
• External Firmware 6.x and above uses an advanced “Host-to-LUN
Mapping” system.
Refer to the appropriate section(s) to follow.