2.3. Configuring ACPI For Use with Integrated Fence Devices

2.3. Configuring ACPI For Use with Integrated Fence Devices

If your cluster uses integrated fence devices, you must configure ACPI (Advanced Configuration and Power Interface) to ensure immediate and complete fencing.

Note

For the most current information about integrated fence devices supported by Red Hat Cluster Suite, refer to http://www.redhat.com/cluster_suite/hardware/.

If a cluster node is configured to be fenced by an integrated fence device, disable ACPI Soft-Off for that node. Disabling ACPI Soft-Off allows an integrated fence device to turn off a node immediately and completely rather than attempting a clean shutdown (for example, shutdown -h now). Otherwise, if ACPI Soft-Off is enabled, an integrated fence device can take four or more seconds to turn off a node (refer to note that follows). In addition, if ACPI Soft-Off is enabled and a node panics or freezes during shutdown, an integrated fence device may not be able to turn off the node. Under those circumstances, fencing is delayed or unsuccessful. Consequently, when a node is fenced with an integrated fence device and ACPI Soft-Off is enabled, a cluster recovers slowly or requires administrative intervention to recover.

Note

The amount of time required to fence a node depends on the integrated fence device used. Some integrated fence devices perform the equivalent of pressing and holding the power button; therefore, the fence device turns off the node in four to five seconds. Other integrated fence devices perform the equivalent of pressing the power button momentarily, relying on the operating system to turn off the node; therefore, the fence device turns off the node in a time span much longer than four to five seconds.

To disable ACPI Soft-Off, use chkconfig management and verify that the node turns off immediately when fenced. The preferred way to disable ACPI Soft-Off is with chkconfig management: however, if that method is not satisfactory for your cluster, you can disable ACPI Soft-Off with one of the following alternate methods:

  • Changing the BIOS setting to "instant-off" or an equivalent setting that turns off the node without delay

    Note

    Disabling ACPI Soft-Off with the BIOS may not be possible with some computers.

  • Appending acpi=off to the kernel boot command line of the /boot/grub/grub.conf file

    Important

    This method completely disables ACPI; some computers do not boot correctly if ACPI is completely disabled. Use this method only if the other methods are not effective for your cluster.

The following sections provide procedures for the preferred method and alternate methods of disabling ACPI Soft-Off:

  • Section 2.3.1, “Disabling ACPI Soft-Off with chkconfig Management” — Preferred method

  • Section 2.3.2, “Disabling ACPI Soft-Off with the BIOS” — First alternate method

  • Section 2.3.3, “Disabling ACPI Completely in the grub.conf File” — Second alternate method