Getting to know which Hyper-V guest is using disk using PowerShell script

Best way to investigate disk usage on hyper-v host is to look at all guests and figure out, which one is exhausting the system. The only way to get those readings is using perfmon (Performance Monitor) Hyper-V specific counters. Simple Task Manager or Resource Monitor doesn’t give that detail.

I got even further and scripted this. First take a look at the script:

$date = Get-Date

"importing AD module"

import-module activedirectory

"Getting computer list from AD"

$servers = Get-ADComputer -LDAPFilter "(operatingsystem=*server*)" | sort name

$servers |  measure

$i=1

write-host "Getting Hyper-V Disk Activity information..."

$info = $servers | foreach {

    $computername = $_.name

    write-host ($i++) $computername

    $readcounter = "\\" + $computername + "\Hyper-V Virtual Storage Device(*)\Read Bytes/sec"

    (get-counter -Counter $readcounter).countersamples | foreach {

        $obj = new-object psobject

        $obj | add-member noteproperty Host ($computername)

        $obj | add-member noteproperty Access ("Read")

        $obj | add-member noteproperty VHD ($_.InstanceName)

        $obj | add-member noteproperty MBps ([Math]::Round($_.CookedValue/1024/1024,2))

        $obj

        }

    $writecounter = "\\" + $computername + "\Hyper-V Virtual Storage Device(*)\Write Bytes/sec"

    (get-counter -Counter $writecounter).countersamples | foreach {

        $obj = new-object psobject

        $obj | add-member noteproperty Host ($computername)

        $obj | add-member noteproperty Access ("Write")

        $obj | add-member noteproperty VHD ($_.InstanceName)

        $obj | add-member noteproperty MBps ([Math]::Round($_.CookedValue/1024/1024,2))

        $obj

        }

    }

$filename2 = "c:\serverinfo\HVdiskactivity {0}.{1:d2}.{2:d2} {3:d2}.{4:d2}.csv" -f $date.year,$date.month,$date.day,$date.hour,$date.minute

# $info | Export-Csv -Path $filename2 -encoding utf8

$info2 = $info | where {$_.MBps -ge 1} | sort MBps -Descending

$info3 = $info2 | ConvertTo-Html

$info4 = [string]$info3

if($info2){

Send-MailMessage -SmtpServer smtp.domain.com -To rauno.magi@domain.com -From rauno.magi@domain.com -Subject "Hyper-v guests having greatest VHD activity" -Body $info4 -BodyAsHtml

}

What does this script do? Let’s look at step by step:

1. First it import’s Active Directory module and uses it to get the list of all servers, which will be recorded to variable $servers


2. Then it uses this list of servers to query performance information on each of them using get-counter cmdlet. It would be nice to reduce the list to hyper-v server’s only, but this is cosmetical and performance issue and doesn’t affect the functionality


3. Nice thing is creating a new empty object and populate all properties/rows with data got from new-object cmdlet.


4. All the information gathered will be stored into $info variable, which can be optionally saved to a csv file. This command is commented out at the moment


5. Filtered and sorted list (disk activity more than 1MB per second, biggest numbers on top) will be sent as a e-mail message attachment in the message body.