Adaptec 1966600 User Guide - Page 65

Important Information About SAN Environments

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Installing the DuraStor Storage Subsystem Important Information About SAN Environments In configurations where there are multiple paths from the host server to the DuraStor, each partition (defined as a FC LUN) is presented to the host as many times as there are paths. For example, if there are two paths from the host to the DuraStor, each partition is seen by the host two times; if there are four paths, each partition is seen four times, and so on. See Figure 3-27 through Figure 3-30 for examples. To prevent the operating system on the host from being confused by the redundant instances of each partition, they must be masked out by using an FC HBA that offers LUN masking. This feature hides the redundant instances of each partition from the operating system on the host server until the primary path fails. ! Caution: In a multi-path SAN environment, you must use FC HBAs that offer LUN masking; otherwise, the host operating system will see the redundant instances of each partition. If the host operating system attempts to write to the redundant instances of the same partition on the DuraStor, it will likely cause data corruption or loss. Figure 3-27 Two Data Paths - Example A Figure 3-28 Two Data Paths - Example B 3-31

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3-31
Installing the DuraStor Storage Subsystem
Important Information About SAN Environments
In configurations where there are multiple paths from the host
server to the DuraStor, each partition (defined as a FC LUN) is
presented to the host as many times as there are paths. For
example, if there are two paths from the host to the DuraStor, each
partition is seen by the host two times; if there are four paths, each
partition is seen four times, and so on. See
Figure 3-27
through
Figure 3-30
for examples.
To prevent the operating system on the host from being confused
by the redundant instances of each partition, they must be
masked
out by using an FC HBA that offers LUN masking. This feature
hides the redundant instances of each partition from the operating
system on the host server until the
primary
path fails.
Caution:
In a multi-path SAN environment, you must use
FC HBAs that offer LUN masking; otherwise, the host
operating system will see the redundant instances of each
partition. If the host operating system attempts to write to
the redundant instances of the same partition on the
DuraStor, it will likely cause data corruption or loss.
Figure 3-27
Two Data Paths - Example A
Figure 3-28
Two Data Paths - Example B
!