In a previous post in this series (see PowerCLI & vSphere statistics – Part 2 – Come together), I showed the usefulness of the Group-Object cmdlet when working with statistical data. The script in that post grouped data samples for each hour together, which made it much easier to calculate the hourly average. With the Group-Object cmdlet you avoid numerous nested if- or switch-statements.
And best of all, you don’t have to code the grouping yourself, it was all done for you by the PowerShell Team.
So make sure this cmdlet belongs to your basic PowerShell repertoire. It will prove invaluable when processing statistical data.
This post will show you several of the different options you have to group statistical data together. And I will illustrate each of these with a sample script.
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In PowerCLI & vSphere statistics – Part 1 – The basics I briefly mentioned instances. In this post I’ll go a bit deeper into that subject.
And to demonstrate it all I will use part of the esxtop post on Yellow Bricks. In that post Duncan compiled, from various sources, a number of “common sense” thresholds that you can use in esxtop to show you possible problems with your hosts and/or guests.
Since I’m not sitting 24/7 behind an ESX/ESXi console, I looked for a way to let PowerCLI/PowerShell do that for me 
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The end of my previous post in this series, see PowerCLI & vSphere statistics – Part 1 – The basics, showed how you could get the statistical values for a specific day.
Depending on the point in time for which you request the values, the sampling interval will be different. For example Historical Interval 2 will return values measured over 30 minute intervals. See also the schematic I included in the previous post.
This sample interval is not always what you want for your reports. Suppose you want to always report hourly values and only for working hours during business days. This post will show you how to accomplish that.
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Another popular subject in the VMTN PowerCLI community are statistics. Quite often it’s not entirely clear to the user what is available, how the data can be extracted and how PowerShell/PowerCLI can be used to convert the raw metrics into usable reports.
Before you can fully use all that is available, there are a few key concepts that you should understand.
In this series I will try to explain some common questions.
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