Powercli Script to Unmount and Detach Datastores

Written by Luke Arntz on May 14, 2019
[ VMware ] [ PowerCLI ] [ PowerShell ]



A storage migration is eventually going to get to a phase where the old datastores need to be unmounted and detached from hosts. I found a script showing how to do this via PowerCLI, but I wanted to expand on it to better serve my use case.

What I came up with is below and also on my github.

When running the script you must specify the vCenter name and the folder containing the datastores that will be unmounted. A regular expression is used to specify the names of the datastores you want to unmount. For example, “Datastore\d\d” would unmount datastores named DATASTORE01 and DATASTORE99, but not DMZ_STORAGE01 (the PowerShell -match operator is not case sensitive). Also, the script will only work on datastores that have been put into maintenance mode.


  • The VMware PowerCLI PowerShell module must be installed.
  • You must be connected via Connect-VIServer to the vCenter containing the datastores you intend to unmount.
  • Datastores must be removed from datastore clusters.
  • Datastores must be in maintenance mode.
  • Datastores must be moved to the same datastore folder.

The Script

A script to unmount and detach datastores from VMWare vCenter.

This script unmounts datastores from vCenter if they are in maintenance mode, reside in the specified folder, and the name matches the specified regular expression.

The VMware PowerCLI module is required and a connection to vCenter (Connect-VIServer) must be established before running the script.

Unmount-Datastores.ps1 -VIServer vcenter.domain.local -NameRegex "Datastore\d\d" -Folder "Unmount"
This command will unmount and detach datastores in the vcenter.domain.local vCenter that reside in the datastore folder named Unmount with names that -match the regular expression "Datastore\d\d".

Author: Luke Arntz
Date:   May 13, 2019



    # Specifies a vCenter server name.
    # Specifies a datastore folder name.
    # Specifies a regular expression to -match datastore names.

$MaintenanceModeDatastores = Get-Datastore -Location (Get-Folder -Name $Folder) -Server $ViServer | where {$_.State -eq "Maintenance" -And $_.Name -match $NameRegex}

$UnMounted = @()
foreach ($MaintenanceModeDatastore in $MaintenanceModeDatastores)
        $datastoreHostInfo = Get-VmHost -Server $viserver -Id ($MaintenanceModeDatastore.ExtensionData.Host.Key)
        $CanonicalName = $MaintenanceModeDatastore.ExtensionData.Info.Vmfs.Extent[0].Diskname
        Write-Host "Processing $($MaintenanceModeDatastore)..."
        foreach ($vmHost in $datastoreHostInfo)
                $unmount = [PSCustomObject]@{
                        Datastore = $MaintenanceModeDatastore.Name
                        DsUuid = $MaintenanceModeDatastore.ExtensionData.info.Vmfs.uuid
                        LunUuid = (Get-ScsiLun -Server $viserver -VmHost $vmHost | where {$_.CanonicalName -eq $CanonicalName}).ExtensionData.Uuid
                        Host = $vmHost.name
                        CanonicalName = $CanonicalName
                        UnmountTime = $null             

                $hostMountInfo = $MaintenanceModeDatastore.ExtensionData.Host | Where {$_.Key -eq $VMHost.Id}
                if($hostMountInfo.MountInfo.Mounted -eq "True")
                        Write-Host "Unmounting $($unmount.Datastore) from host $($VMHost.Name)"
                        $hostStorageSystem = Get-View $VMHost.Extensiondata.ConfigManager.StorageSystem
                } else {
                        write-host "$($unmount.Datastore) not mounted on $($VMhost.Name)"

                $unmount.UnmountTime = Get-Date -Format "s"
                $UnMounted += $unmount


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