OVH Servers affected by known Citrix bug CTX127395

Posted abril 9th, 2012 in Blog, Virtualization and tagged , , , , by Alfredo

If you have some XenServer 5.6 host that randomly (and suddenly) becomes completely unresponsive with no apparent reason, then it might be affected by an odd bug that has been documented by Citrix.

Is my server affected?

Potentially, any server based on the Nehalem (Xeon 75xx, 55xx, 35xx, 34xx) and Westmere (Xeon 56xx, 36xx) architectures can be affected.

How to know if my XenServer 5.6 is affected?

  1. Open a console to your XenServer host (SSH client, the console tab in XenCenter, or the local console).
  2. Make sure that your server is running on any of the affected architectures. To find out, run:
  3. If it is,  with administrative privileges run:

If the value of total C-States is bigger than 2, then this server is affected by the bug and if necessary, they must be disabled from the BIOS.

How to fix?


If you have KVM available, complete the following procedure:

  1. Reboot the server and go in BIOS setup.
  2. In the BIOS menu, set the value for the C-states option to Disabled.
  3. In the BIOS menu, set the value for the Turbo Mode option to Disabled.
  4. If the server BIOS has power management options that leave power management to the BIOS rather than the operating system, such as Active Power Controller mode of Dell, then disable this option and set the power management options to OS Control.

If you do not have KVM attached to your affected server, then you will have to generate a technical incident to your Data Center, requesting to apply the just described procedure.


Citrix links related to this issue:

Leave a Reply