Adaptec 1542B - AHA Storage Controller Fast SCSI 10 MBps Spezifikationen PDF herunterladen (Seite 33)

Chapter 6

Redundant DPU Operation

Overview

In a redundant configuration, two DPUs are connected to form a backup pair.

One DPU is designated as the primary unit and the other DPU the secondary

unit. The IP address of the secondary DPU is always one number greater than

the address of the primary DPU. The Primary is always the even address

while the Secondary is the odd address.

The installation, preparation, and adjustment procedures included in this

publication apply to both DPUs in a redundant configuration. This chapter

provides information on switches and cabling in a redundant configuration.

Automatic Failover / Manual Takeover

Process control can be transferred between DPUs in a backup pair either

automatically (Failover), or by manual command (Takeover). Automatic

Failover can occur from either the primary DPU to the secondary DPU or

from the secondary to primary based on the health of each DPU. Manual

failover does not depend upon the relative health of the DPUs.

Automatic Failover

Process control is automatically transferred from the active DPU to the

inactive DPU when the active DPU experiences a severe diagnostic alarm or

when communication between active and inactive DPU is lost. However, if

the inactive DPU is itself experiencing a severe diagnostic alarm, it will

refuse control, unless the active DPU loses power or is reset.

In general, each DPU calculates a value for its “health”. The health value

depends on a number of things including network errors, I/O errors and

backup link errors. An inactive DPU will not automatically take over control

from an active DPU if the health of the inactive is less than the health of the

active DPU.

Manual Takeover

To manually command either DPU to assume control, press the Takeover

button on the front panel of the inactive DPU. Manual takeover will occur

only if the inactive DPU is “hot” (has a good copy of the active DPU’s

Metso Automation • 278590 •

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Adaptec 1542B - AHA Storage Controller Fast SCSI 10 MBps Spezifikationen Seite 33