APC RAID Subsystem SCSI-SATA II Informações Técnicas descarregar pdf (Página 128)

Advanced Functions

5-10

5.2 Multiple ID solutions

5.2.1 Overview

The multiple ID mechanism provides host transparent controller failover/failback solution. That is, no particular software

or driver is required to be installed at the host side. Howerver, a fiber switch is required. Through the connection of fiber

switch, the fiber host chanel ports can provide backup for each other. ‘Fcpa1’ and ‘fcpb1’ can backup each other, so do

‘fcpa2’ and ‘fcpb2’.

For example, if controller A fails, ‘fcpb1’ inherits the target ID of ‘fcpa1’, while ‘fcpb2’ inherits the target ID of ‘fcpa2’. When

the target ID is inherited, the lun-map under the ID is inherited as well. Now, both ‘fcpb1’ and ‘fcpb2’ have two IDs. When

controller A gets failback, ‘fcpb1’ and ‘fcpb2’ disable the inherited ID before ‘fcpa1’ and ‘fcpa2’ are enabled. The

procedure is delicately controlled to achieve seamless failover/failback.

When MTID mode is selected, the topology is set to arbitration loop automatically. The fiber switch ports connected to the

RAID fiber ports should be configured as public loop ports which are often denoted as FL or GL ports. The target loop ID

can be changed manually to avoid conflict with initiator loop ID if a simple fiber hub is used.

At the moment, only FC RAID system supports multiple ID solutions.

As Figure 5-5 shows, the green and the red dotted paths are both active paths. When the green path link fails, the red

dotted path will continue to access all the storage devices without interruption.

To set up the connection, perform these tasks in the RAID GUI:

• Create virtual volumes and specify the preferred controllers

• Specify the storage provisioning method

• Specify the LUN ID and map LUNs to fiber ports

The succeeding Configuration Tasks table shows the details of each configuration task according to the example given in

Figure 5-5.

Loop2Loop1

FCP1FCP2FCPa2 FCPa1

(DG0LD0) (DG0LD1)

FCP1FCP2FCPb2 FCPb1

FC Switch

Controller A

(DG1LD0) (DG1LD1)

Controller B

WWPN

HBA1HBA0

Server (without

pathguard installed)

Host Group 0

Figure 5-5 MTID environment

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