[mrtg] Re: Weird CPU Graphs

[Jerry Heidtke]

See http://support.microsoft.com/support/kb/articles/q146/0/04.asp

Microsoft's side of the story:

SNMP Counter Values Are Unreliable in SMP Computers
The information in this article applies to:Microsoft Windows 2000 Server
Microsoft Windows 2000 Advanced Server
Microsoft Windows 2000 Professional
Microsoft Windows 2000 Datacenter Server
Microsoft Windows NT Server 3.5
Microsoft Windows NT Server 3.51
Microsoft Windows NT Server 4.0
SYMPTOMS
Windows NT simple network management protocol (SNMP) counters, such as
output queue length, may yield unlikely results in symmetric
multiprocessor (SMP) computers.
CAUSE
This problem occurs because Windows NT TCP/IP does not use interlocked
operations to maintain its statistics counters. The SNMP counters are
maintained in the TCP/IP code.
The decision to not implement spinlocks to guarantee the integrity of
the SNMP counters is based on performance concerns and will not be
changed. 
STATUS
Spinlocks were left out of the TCP/IP code for counter operations
intentionally for performance reasons. This will not be fixed. 

My side of the story:

Microsoft has never been serious about snmp support in their operating
systems, because having properly implemented snmp support for monitoring
and management enables users to implement someone else's products for
management and monitoring. Microsoft wants you to use their expensive
and proprietary products.

It is possible to get reliable statistics out of Windows for use in
MRTG, but you won't do this through Microsoft's snmp. If your hardware
vendor supplies snmp management agents, use those, otherwise do
something like directly query WMI stats with an external vbscript
program run through mrtg.

Jerry

 

-----Original Message-----
From: Anthony Scott [mailto:ascott at triadfoodsgroup.com] 
Sent: Wednesday, April 16, 2003 7:47 AM
To: MRTG (E-mail)
Subject: [mrtg] Weird CPU Graphs


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Hi all. I am monitoring CPU Utilization a dual processor Win2k Server. I
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am using MRTG with RRDTool and I am getting some really strange results.
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I have attached a pic but I don't know if it will go through.
Basically, I used GetIf to get the OIDs for each processor. I am getting
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consistent spike to 100% on the second CPU and very erratic results for
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the first cpu. Windows performance monitor display more normal results.
Any ideas?
Thanks!!



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