Overview Of Failover Drivers; Failover Driver Setup Considerations - Silicon Graphics InfiniteStorage 4000 Series User Manual

Overview of Failover Drivers

Failover Driver
Setup
Considerations
Chapter 1: Overview of Failover Drivers
Failover drivers provide redundant path management for storage devices and cables in
the data path from the host bus adapter to the controller. For example, you can connect
two host bus adapters in the system to the redundant controller pair in a storage array,
with different buses for each controller. If one host bus adapter, one bus cable, or one
controller fails, the failover driver automatically reroutes input/output (I/O) to the
good path, which permits the storage array to continue operating without interruption.
Failover drivers provide these functions:
They automatically identify redundant I/O paths.
They automatically reroute I/O to an alternate controller when a controller fails
or all of the data paths to a controller fail.
They check the state of known paths to the storage array.
They provide status information on the controller and the bus.
They check to see if the Service mode is enabled and if the modes have switched
between Redundant Dual Active Controller (RDAC) and Auto-Volume Transfer
(AVT).
They check to see if Service mode is enabled on a controller and if the AVT or
asymmetric logical unit access (ALUA) mode of operation has changed.
Most storage arrays contain two controllers that are set up as redundant controllers. If
one controller fails, the other controller in the pair takes over the functions of the
failed controller, and the storage array continues to process data. You can then replace
the failed controller and resume normal operation. You do not need to shut down the
storage array to perform this task.
The redundant controller feature is managed by the failover driver software, which
controls data flow to the controller pairs independent of the operating system (OS).
This software tracks the current status of the connections and can perform the
switch-over without any changes in the OS.
Whether your storage arrays have the redundant controller feature depends on a
number of items:
Whether the hardware supports it. Refer to the hardware documentation for your
storage arrays to determine whether the hardware supports redundant controllers.
Whether your OS supports certain failover drivers. Refer to the installation and
support guide for your OS to determine if your OS supports redundant
controllers.
How the storage arrays are connected. The storage array must have two
controllers installed in a redundant configuration. Drive trays must be cabled
correctly to support redundant paths to all drives.
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