Installation guide

Glossary
G-4 GAM Client v3.00 and WSAM User’s Manual
External RAID Operation
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.
External RAID Controller
The controller acts as a bridge between host channels and drive channels,
and implements the RAID function. On the drive channels, the controller
acts as an initiator. The host channel ports are implemented as target IDs,
with logical drives presented as LUNs under the target IDs.
Host to LUN Mapping
The host to LUN mapping feature is intended for use in configurations in
which multiple host computers attach to one or more Mylex controllers. This
is also referred to as a Storage Area Network (SAN) configuration. The host
to LUN mapping feature restricts host access to configured system drives.
Access to a configured system drive is granted only to a single host or group
of hosts.
Hot Replacement of Disks (“Hot Swap”)
The design of Mylex RAID controllers allows for the replacement of failed
hard disk drives without interruption of system service. In the event of a
drive failure on a properly configured system (where the data