Rackable Systems OmniStor 4900F Series, User Manual

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Chapter 2 - Topologies and Operating Modes
Alternate Path Software
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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.