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SN0054651-00 F 2-5
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RAID Configuration and LUN Masking
Figure 2-4 illustrates the interaction of an adapter alternate with a LUN alternate in
a RAID subsystem. Two hosts (X and Y) connect to a fabric, which is simplified for
this diagram. Also on the fabric is a RAID subsystem with dual controllers (left and
right) containing eight LUNs.
Figure 2-4 RAID Configuration and LUN Masking
Figure 2-4 is a generic example of a RAID configuration. Many, but not all, RAID
systems operate in this manner. The following paragraphs describe this
configuration:
All hosts and storage devices are connected to a common fabric. Details of
fabric configuration are not important, except to note that all hosts and
adapters can connect to all storage devices. Depending on the fabric, some
devices may appear on the local loop and as fabric devices.
Hosts X and Y must be configured to recognize different target devices or
else risk overwriting each other's data. SANsurfer FC HBA Manager must be
run on each host to configure devices as enabled (with a preferred and
alternate path assigned to each device) or disabled.
If hosts X and Y are cooperating in a cluster, they can be configured so that
both recognize a specific device. In this case, clustering software and the
clustered application must determine which host is permitted to write to the
device.
Host X
A
B
Host Y
LUNs 0–3
LUNs 4–7
A
B
Left
Right
RAID
System
LUNs 0–7
Fabric
Controllers
Adapters
Adapters