Red Hat ENTERPRISE LINUX 5 - ADMINISTRATION Manual page 23

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"
•
Section 2.3.2, "Disabling ACPI Soft-Off with the BIOS"
•
Section 2.3.3, "Disabling ACPI Completely in the grub.conf File"
•
Configuring ACPI For Use with Integrated Fence Devices
— First alternate method
— Preferred method
— Second alternate method
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