Windows Server 2008 R2 and Core Parking, how it affects you, the administrator.
Applies to:
Windows Server 2008 R2 Service Pack 1
Windows Server 2008 R2 SP1
Windows Server 2008 R2 RTM (a.k.a. Gold)
Symptoms:
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Your Windows Server 2008 R2 RTM/SP1 hosting Hyper-V/File/Print/SQL/Exchange/Sharepoint/SCCM/SCVMM/SCOM/Lync etc… feels sluggish.
You might see high cpu or slow disk i/o
In Task Manager, you might see something similar to:
In Resource Monitor, you might notice the “Parked” next to the different CPU’s.
The issue is that with increased loads, the CPU should un-park themselves and go back to work.
Solution:
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1) You want to make sure that the bios is up to date.
The processor manufacturers have provided your server hardware manufacturers with firmware updates that help manage the C-States.
2) Hotfixes for W2K8 R2 Hosts and guests:
2534356 Some CPU cores are parked while other active CPU cores have a heavy workload in Windows Server 2008 R2
If using AMD CPU’s:
2645594 An update is available for computers that have an AMD FX, an AMD Opteron 4200, or an AMD Opteron 6200 series processor installed and that are running Windows 7 or Windows Server 2008 R2
3) Result if you do not update the bios, or install the patches:
2207548 Degraded overall performance on Windows Server 2008 R2
https://support.microsoft.com/?id=2207548
2254067 You may notice increased IO latencies that impact performance when power management is enabled.
4) Some customers decided to just set the Power Plan from "Balanced" to “High Performance” which disables Core Parking.
2646060 An update that selectively disables the Core Parking feature in Windows 7 or in Windows Server 2008 R2 is available
https://support.microsoft.com/?id=2646060
Note: This (steps 3 and 4 in the beginning of Windows Server 2008 R2) was the advice provided, but no longer recommended.
So what should I do as an administrator?
Have both features, save money in power and have the performance that you need.
Go thru steps 1 and 2, and you should see the overall benefit of “Core Parking” and still get good throughput.
More information about "Core Parking":
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Windows 7 / Windows Server 2008 R2: Core Parking / Intelligent Timer Tick / Timer Coalescing
Core parking in Server 2008 R2 – why it’s like airport X-ray machines.
Windows Server 2008 R2 Hyper-V and AMD's 6-core Opteron
https://sqlserverperformance.wordpress.com/2010/09/28/windows-power-plans-and-cpu-performance/