Comments on: Inaccuracy of In-guest Performance Counters

By: drummonds

drummonds — Sat, 24 Sep 2011 08:11:44 +0000

Casey,

If the only question you are trying to answer is, “Is my application resource-contrained?” then it does not matter if the counters are accurate or not. But there are other questions that require more accurate counters:

How much CPU is available on the host? (Estimating this using tools that collate guest counters will produce inaccurate results.)
How much CPU is application “X” using? (As the article states, guest tools are inaccurate.)

So, there are some questions that require accurate answers. But, as you point out, some questions are simple enough that guest tools are sufficient.

By: Casey

Casey — Fri, 23 Sep 2011 18:41:59 +0000

I have a question…based on your explanations, what does it matter? If the OS says it has no resources left, and throttles back the applications, does it matter that the OS isn’t right?

By: Matt

Matt — Fri, 12 Nov 2010 05:09:43 +0000

Great explanation and I’d prefer to use these stats for our monitoring system, however each time the VM counters are used the vmStatsProvider generates 2 events to the application log, EventIDs: 256 and 258, which just say the wmi stats provider has been initialized. So, as we poll the counters every 5 minutes it floods the event log with thousands of events a day. A way to suppress these rather useless informational events would make life easier.

By: Tim Kresler

Tim Kresler — Fri, 06 Aug 2010 14:14:00 +0000

Great post, Scott. It really shows how collecting data from multiple spots (Guest OS for Memory utilization data, and it’s view of CPU utilization), vSphere for VM memory and CPU utilization and host overhead is key. If you only look at the system from one perspective, your view is easily skewed. You need a multi-dimensional approach to ensure you are getting the right information.

By: Gul

Gul — Wed, 21 Jul 2010 19:26:19 +0000

Great job! I have been in the virtualization field for years and get tired of explaining this. You’ve done a spectacular job at bringing the details to the table in a way that the average user can understand. Applause.

By: drummonds

drummonds — Wed, 12 May 2010 23:47:44 +0000

There are not good active memory counters in any operating systems that I am aware of. For that I always prefer vSphere’s tools. But it is true that vSphere knows nothing about how the memory is being used: process memory, IO buffers, kernel memory, etc. So, some guest counters are useful in troubleshooting and capacity management.

Scott

By: Dave

Dave — Mon, 10 May 2010 21:32:49 +0000

I’m curious about how you feel this applies to memory utilization.

I agree the Anonymous user that posted about trusting CPU utilization in the right context.

Ballooning, host swapping and TPS will skew the memory readings in the guest, but these do not always apply. In an environment where there is little to now ballooning or swapping, one only needs to consider TPS.

In fact, one might argue that the guest memory counters can be more accurate because ESX only knows what memory has been consumed/granted or has been accessed recently (active)… In the case where an application does a lot of caching, it may be important to know that this memory is actually allocated.

By: RTFM Education » Blog Archive » vNews – Mar, 2010

RTFM Education » Blog Archive » vNews – Mar, 2010 — Thu, 04 Mar 2010 18:38:33 +0000

[...] Microsoft NVSPBIND.EXECitrix release virtual appliances [...]

By: Scott

Scott — Thu, 18 Feb 2010 00:23:44 +0000

You are right! I corrected the image order.

By: michael

michael — Wed, 17 Feb 2010 15:45:36 +0000

thanks for a post.
you should change the order of the screenshots.