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Intermittent 100% CPU sur all VMs

ayi

We’re a small shop, running a Dell T420 (dual CPU, only one present, 6 cores) w/32GB RAM as our main server. Nous avons only 5 VMs, one of which is our WSE 2012 DC.
From time to time, and at a rate for which we’ve not been able to establish a reliable pattern, all of our VMs concurrently spike to 100% CPU. The host remains quiet at 4-5%. A host warm boot doesn’t provide relief, but a cold boot au moins puts things back in the box until le problème reoccurs.
Sometimes we can get a week or more of calm seas out of it; sometimes only a day. An unreliable pattern seems to be that it kicks off sometime during an extended idle period, i.e. overnight. An examination of le serveur’s temperature logs first led us to suspect overheating, but further investigation into recent incidents have spoiled that lead.
We also found descriptions of similar problems on the Dell forums, with claims of resolution by installing the latest round of Dell updates. We recently engaged in a project to do just that (as an aside, it was quite an adventure getting _700GB of VHDs safely off of and then back onto that machine), but to our utter dismay it didn’t help.
We’re absolutely befuddled. So is Microsoft support (or au moins first tier support is, even though they try not to act like it). I’m including below our SystemInfo output.
Quelqu’un sait-il where to start looking?
Merci
===================================
Host Name: SERVER1 
OS Name: Microsoft Hyper-V Server 2012 R2 
OS Version: 6.3.9600 N/A Build 9600 
OS Manufacturer: Microsoft Corporation 
OS Configuration: Standalone Server 
OS Build Type: Multiprocessor Free 
Registered Owner: Windows User 
Registered Organization: 
Product ID: 06401-029-0000043-76293 
Original Install Date: 4/3/2014, 4:07:15 PM 
System Boot Time: 5/4/2014, 1:56:47 PM 
System Manufacturer: Dell Inc. 
System Model: PowerEdge T420 
System Type: x64-based PC 
Processor(s): 1 Processor(s) Installed. 
01: Intel64 Family 6 Model 45 Stepping 7 GenuineIntel ₂₂₀₀ Mhz 
[Intel(R) Xeon(R) CPU E5-2430 0 @ 2.20 GHz] (manually added) 
BIOS Version: Dell Inc. 2.1.2, 1/20/2014 
Windows Directory: C:\Windows 
System Directory: C:\Windows\system32 
Boot Device: \Device\HarddiskVolume1 
System Locale: en-us;English (United States) 
Input Locale: en-us;English (United States) 
Time Zone: (UTC-09:00) Alaska 
Total Physical Memory: 32,723 MB 
Available Physical Memory: 12,716 MB 
Virtual Memory: Max Size: 37,587 MB 
Virtual Memory: Available: 17,129 MB 
Virtual Memory: In Use: 20,458 MB 
Page File Location(s): C:\pagefile.sys 
Domain: OIT 
Logon Server: \SERVER1 
Hotfix(s): 31 Hotfix(s) Installed. 
Network Card(s): 3 NIC(s) Installed. 
01: Broadcom NetXtreme Gigabit Ethernet 
Connection Name: NIC1 
DHCP Enabled: No 
IP address(es) 
02: Broadcom NetXtreme Gigabit Ethernet 
Connection Name: NIC2 
DHCP Enabled: Yes 
DHCP Server: 192.168.1.12 
IP address(es) 
03: Hyper-V Virtual Ethernet Adapter 
Connection Name: vEthernet (External NIC 1_Internal) 
DHCP Enabled: No 
IP address(es) 
Hyper-V Requirements: A hypervisor has been detected. Features required for Hyper-V will not be displayed.
== EDIT ======================
J’ai found la solution to this issue; I waited for over a year to assurez-vous we didn’t encounter any more instances of le problème.
Moderators: J’aimerais to request a reopening of the question, so that I can post the answer.
<hr>
Source : [Server Fault](<a href="http://en.community.dell.com/techcenter/extras/m/white_papers/20161975/download" rel="noopener nofollow ugc">http://en.community.dell.com/techcenter/extras/m/white_papers/20161975/download</a>](<a href="http://en.community.dell.com/techcenter/extras/m/white_papers/20161975/download" rel="noopener nofollow ugc">http://en.community.dell.com/techcenter/extras/m/white_papers/20161975/download</a>)

ayi_2

After over a year of waiting so as to prove la solution as valid, I’m finally able to post this answer.
Dell’s default BIOS settings have C-States enabled, which puts the computer in low-power mode during idle times. This is what causes the VMs to spiral into 100% CPU usage on a Hypervisor host (VMWare, Citrix included).
La solution est to set the System Profile setting in the BIOS to Performance, as opposed to Performance per watt [OS] or Performance per watt [DAPC] (the latter being the default).
The relevant Dell documentation, pp3:
<a href="http://en.community.dell.com/techcenter/extras/m/white_papers/20161975/download">http://en.community.dell.com/techcenter/extras/m/white_papers/20161975/download</a>
And this reply from one of the few Dell support engineers who’s familiar with le problème:
<blockquote></blockquote>
The short version is: C-States disable additional processor cores during idling times. For VMs that are tied to a core (this is OS controlled, I do not believe it’s configurable), this could result in them locking up, as they’re attemping to perform actions with resources that no longer exist in their eyes.
Generally speaking, C-States are generally used on items like backup servers, secondary role servers (Backup dns, dhcp, Domain controllers, etc) so that way the backup servers can remain on, but in a low power mode to save energy.
Addtional Documentation can be found here:
<a href="http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface">http://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface</a>
In a nutshell, power idling on a Dell server should always be turned off (set to Performance) for Hypervisor hosts.
Merci to Eddy Simons at Kitsap Bank for helping me to find this solution.