Which Disk is that volume on?

I administer a server VM with a lot of disks, and many of them are the same size. When I need to make changes to the system’s storage, I’m always nervous that I’m going to poke the wrong disk. I could trust that the order of the disks listed in the vSphere client is the same as the order that the guest OS lists (starting at 1 and 0 respectively). But I want a little more assurance.

Using diskpart, you can list the details for individual disks, partitions and volumes, but I wanted a report showing all the disks, the partitions on those disks, and the volumes residing on those partitions. I have reported some of this info previously, using PowerShell’s Get-WMIObject cmdlet to query the Win32_DiskDrive, Win32_Partition, and Win32_Volume classes. I figured there must me a way to correlate instances of these classes.

I found these two blog posts:

• Scripting Guy’s How Can I Correlate Logical Drives and Physical Disks?
• JRich’s Using WMI to link a Disk Volume to a Physical Disk with PowerShell

They did most of the heavy lifting in building the WQL ASSOCIATOR OF queries. I put together a short script to give me a little more detail. Here’s some sample output:

PS C:\local\scripts> .\Get-DiskInfo.ps1
Disk 0 - SCSI 0:0:2:0 - 45.00 GB
    Partition 0  100.00 MB  Installable File System
    Partition 1  44.90 GB  Installable File System
        C: [NTFS] 44.90 GB ( 3.46 GB free )
[...]
Disk 5 - SCSI 0:0:2:5 - 39.99 GB
    Partition 0  40.00 GB  Installable File System
        B: [NTFS] 40.00 GB ( 34.54 GB free )

This will make it easier to be sure about the vSphere storage element that corresponds to a particular volume (or, more accurately, the Physical Disk on which the volume resides).

Here’s the actual script:

<#
.SYNOPSIS
Get information about the physical disks and volumes on a system.

.DESCRIPTION
Get details about the physical disks and the volumes located on
those disks, to make it easier to identify corresponding vSphere
storage (VMDKs).

.EXAMPLE

PS C:\> .\Get-DiskInfo.ps1

.NOTES
    Author: Geoff Duke <Geoffrey.Duke@uvm.edu>
    Based on http://bit.ly/XowLns and http://bit.ly/XeIqFh
#>

Set-PSDebug -Strict

Function Main {

    $diskdrives = get-wmiobject Win32_DiskDrive | sort Index

    $colSize = @{Name='Size';Expression={Get-HRSize $_.Size}}

    foreach ( $disk in $diskdrives ) {

        $scsi_details = 'SCSI ' + $disk.SCSIBus         + ':' +
                                  $disk.SCSILogicalUnit + ':' +
                                  $disk.SCSIPort        + ':' +
                                  $disk.SCSITargetID
        write $( 'Disk ' + $disk.Index + ' - ' + $scsi_details +
                 ' - ' + ( Get-HRSize $disk.size) )

        $part_query = 'ASSOCIATORS OF {Win32_DiskDrive.DeviceID="' +
                      $disk.DeviceID.replace('\','\\') +
                      '"} WHERE AssocClass=Win32_DiskDriveToDiskPartition'

        $partitions = @( get-wmiobject -query $part_query | 
                         sort StartingOffset )
        foreach ($partition in $partitions) {

            $vol_query = 'ASSOCIATORS OF {Win32_DiskPartition.DeviceID="' +
                         $partition.DeviceID +
                         '"} WHERE AssocClass=Win32_LogicalDiskToPartition'
            $volumes   = @(get-wmiobject -query $vol_query)

            write $( '    Partition ' + $partition.Index + '  ' +
                     ( Get-HRSize $partition.Size) + '  ' +
                     $partition.Type
                   )

            foreach ( $volume in $volumes) {
                write $( '        ' + $volume.name + 
                         ' [' + $volume.FileSystem + '] ' + 
                         ( Get-HRSize $volume.Size ) + ' ( ' +
                         ( Get-HRSize $volume.FreeSpace ) + ' free )'
                       )

            } # end foreach vol

        } # end foreach part

        write ''

    } # end foreach disk

}

#--------------------------------------------------------------------
function Get-HRSize {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$True, ValueFromPipeline=$True)]
        [INT64] $bytes
    )
    process {
        if     ( $bytes -gt 1pb ) { "{0:N2} PB" -f ($bytes / 1pb) }
        elseif ( $bytes -gt 1tb ) { "{0:N2} TB" -f ($bytes / 1tb) }
        elseif ( $bytes -gt 1gb ) { "{0:N2} GB" -f ($bytes / 1gb) }
        elseif ( $bytes -gt 1mb ) { "{0:N2} MB" -f ($bytes / 1mb) }
        elseif ( $bytes -gt 1kb ) { "{0:N2} KB" -f ($bytes / 1kb) }
        else   { "{0:N} Bytes" -f $bytes }
    }
} # End Function:Get-HRSize

Main

Please let me know if you find this helpful.