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3. Disable Extra C-states

3. Disable Extra C-states

Applicable to all Oracle VM 3.x Releases. 
To reduce the risk of unexpected server reboots, extra C-states should be disabled in the BIOS of each Oracle VM Server. If the BIOS has a settings named "Active Power Controller mode", disable this option as well. 
 
The Intel Nehalem CPU introduced a CPU power-saving feature called deep CPU operating states (C-states). C-states allows an idle processor to turn off unused components to save power. Some of the components that C-states turns off include the processor clock and interrupts. Under certain conditions, when C-states turns off unused CPU components, the Oracle VM OCFS2 heartbeat mechanism triggers an unexpected server reboot.
 
C-states server reboots log the following log entries in /var/log/messages. 
 
May  4 16:45:40 <HOST NAME> syslogd 1.4.1: restart.
May  4 16:45:40 <HOST NAME> kernel: klogd 1.4.1, log source = /proc/kmsg started.
 
On alive servers in the pool, the following OCFS2 o2net connection error appear in /var/log/messages.
 
server2 kernel: o2net: Connection to node "<HOST NAME>" (num 0) at xx.xx.xxx.xxx:7777 has been idle for 60.5 secs, shutting it down.
 
To confirm if extra C-states are enabled, as root type:
# xenpm get-cpuidle-states | grep total | uniq
total C-states : 2
 
If the "total C-states" is greater than 2, then extra C-states is enabled in the server's BIOS. The above example shows that extra C-states are disabled on the hosts, i.e. "total C-states : 2".  If extra C-States are enabled, the command output would show: "total C-states: 4"
 

How to Disable Extra C-states on HP Servers:

1. Reboot
2. Enter the BIOS Setup Utility by pressing F9 on POST
3. Navigate to Power Management Option" => Advanced Power Management Options => Minimum Processor Idle Power State
4. Choose "No C-States"
5. To exit the BIOS Setup Utility and save the new settings, press Esc.


How to Disable Extra C-states on SUN x86 Servers:

1. Reboot
2. Enter the BIOS Setup Utility by pressing F2 on POST
3. Navigate to Advanced => CPU Configuration => Intel (R) C-STATE tech => Options
4. Choose "Disabled"
5. To exit the BIOS Setup Utility and save the new settings, press Esc.
 

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