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Chapter 2 - Topologies and Operating Modes
Alternate Path Software
This is a software tool that manages multiple paths between the host operating
system and LUNs (logical drive). The software manages the multiple paths by
detecting duplicate disk objects that represent a single logical drive. It then
designates one disk object as the primary disk object with a primary path, while
the other is designated the secondary disk object with an alternate path. If the
primary path becomes inaccessible, the software redirects the data to the
secondary disk object through the alternate path, preserving the logical drive.
This redirection is known as path failover. The software continuously tries to
access the failed path by issuing a SCSI Test Unit Ready command. A good status
returned indicates the path is repaired and restored to operational status. The
software automatically redirects data back to the primary path and primary disk
object. This restoration of data transfer is known as path failback.
Fibre Channel Media Types
Optical transceivers are provided with the enclosure. Fibre optical transceivers
provides a more reliable media and supports distances up to 300 meters between
nodes.
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Alternate Path Software
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