Compaq HSZ80 manual Selecting a Failover Mode, Using Transparent Failover Mode

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Selecting a Failover Mode

In selecting a failover mode, you have two choices: transparent failover or multiple- bus failover. If you want the failover to occur without any intervention from the host, then transparent failover is best suited. The devices attached to the failed controller fail over to the surviving controller. With multiple-bus failover, the host intervenes during failover and sends commands to the companion controller.

Using Transparent Failover Mode

Transparent failover is a dual-redundant controller configuration in which two controllers are connected to the same host and device buses. Use this configuration if you want to use two controllers to service the entire group of storagesets, single-disk units, and other storage devices. Because both controllers service the same storage units, either controller can continue to service all of the units if its companion controller fails.

Distribute the I/O load between the two controllers in a transparent failover configuration using the following commands to specify which controller handles which targets and units:

SET THIS_CONTROLLER PORT_1_PREFERRED_ID = (n,n)

or

SET THIS_CONTROLLER PORT_2_PREFERRED_ID = (n,n)

Keep the following tips in mind if you configure controllers for transparent failover:

■Set your controllers for transparent failover before configuring devices. By doing this, devices, storagesets, and units added to one controller’s configuration are automatically added to the other controller’s configuration.

■If you decide to configure your devices before setting the controllers for transparent failover, make sure you know which controller has the good configuration information before specifying SET FAILOVER COPY command. See Chapter 5, “CLI Commands,” for details about setting the failover.

Compaq HSZ80 Array Controller ACS Version 8.3 Configuration and CLI Reference Guide