Infortrend RAID Controller Manual

configuration of drives to LUNs under either ID and thus divide or
distribute the workload specifically to different controllers.
Figure 12 - 6 Mapping System Drives (IDs)
Some operating systems do not read multiple LUNs under single SCSI
ID. As diagrammed above, you may create multiple IDs on the host
channel and map logical configurations to these IDs. Each of these
IDs can be designated as Primary or Secondary. Units mapped to
Primary IDs will be managed by the Primary controller, and those
mapped to Secondary IDs Secondary controller. As a rule, each unit
will be mapped to LUN0 under each SCSI ID.
12.1.3 Fault-Tolerance
Hardware failures can occur. A simple parity error may sometimes
cause a RAID system to completely hang up. However, system down
time is not allowed for today's mission-critical environment. Having
two controllers working together will guarantee that at least one
controller will survive the catastrophes and keep the system working.
This is the logic behind having redundant controllers – to minimize
the best we could the chance of down time for a storage system.
Redundant controller means using two controllers in a RAID system.
The redundant controller configuration requires two controllers and
both must be working normally. During normal operation, each
controller serves its own I/O requests from the host. If one controller
Redundant Controller 12-5