Cannot access Volume Shadow Copy until it is accessed via GUI [powershell]

Question

I'm writing a simple powershell script that would automate offsite backup from Windows file server to another remote Windows server. Files might be in use, so in order for Robocopy to sucessfully copy them I need to copy the files from last available Volume Shadow Copy for that specific drive.

I can find the last Shadow Copy with Powershell just fine; the problem is that I cannot actually "referece" it (mount it) in order to access files on the Shadow Copy.

But this "magically" changes if I first access contents of the Shadow Copy via Windows Explorer GUI

Then all of the sudden, I can access the Shadow Copy just fine and copy the contents to a remote backup server.

Here's the code in question:

#Find the latest Shadow copy
$HDDriveID = (Get-WmiObject win32_volume -filter "DriveLetter='E:'").DeviceID
$LastShadowCopy = Get-WmiObject win32_shadowcopy | Where-Object {$_.VolumeName -eq $HDDriveID} | Sort-Object InstallDate | Select-Object -Last 1

# And parse the path so that we can mount it
$arr = $LastShadowCopy.InstallDate.Split('+').Split('.')
$VolumeShadowCopytime = [DateTime]::ParseExact($arr[0], 'yyyyMMddHHmmss', $null)
$UTCTime = $VolumeShadowCopytime.AddHours(-[int]$arr[2]/60)
$VolumeShadowCopyPath = "\\127.0.0.1\E$\@GMT-" + (Get-Date $UTCTime).ToString("yyyy.MM.dd-HH.mm.ss") + "\"

# Then, let's actually mount it:
New-PSDrive -Name Y -PSProvider FileSystem -Root $VolumeShadowCopyPath

If I run this part of a script without accessing the last Shadow Copy via GUI, I receive the following error:

New-PSDrive : The specified drive root "\\127.0.0.1\E$\@GMT-2018.06.27-05.00.09\" either does not exist, or it is not a folder.
At [scriptlocation]\BackupToAzureDrive.ps1:21 char:1
+ New-PSDrive -Name Y -PSProvider FileSystem -Root $VolumeShadowCopyPat ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ReadError: (Y:PSDriveInfo) [New-PSDrive], IOException
    + FullyQualifiedErrorId : DriveRootError,Microsoft.PowerShell.Commands.NewPSDriveCommand

Again, as soon as the Shadow copy is (aparently?) properly referenced by Windows when I open it via Windows Explorer, I get no such error. Shadow Copy gets mounted without any problems and I can access files&folders.

I'm no Powershell guru nor am I very enthusiastic about it. I'm stuck with this problem for days now. Does anyone have an idea how to solve this and/or knows of the workaround?

Answer 1

Upon looking at this stackoverflow question here I got my answer. I've come across this answer earlier but I dismissed it because it suggest using mklink to "map" a VS Copy and not the native New-PSDrive. In fact I've glanced over the answer too quickly and missed the crucial advice. My bad. Kudos to the guy answering it the first time, Ansgar Wiechers.

Anyway, it seems that the correct way to reference the Shadow Copy is to first select the desired Shadow copy and then accessing the DeviceObject Property. This way my code required to map the specific Shadow Copy is down to three lines (and yes, it can most probably be reduced even further (and converted to CIM instead od WMI)):

#Find the latest Shadow copy
$HDDriveID = (Get-WmiObject win32_volume -filter "DriveLetter='E:'").DeviceID
$LastShadowCopy = Get-WmiObject win32_shadowcopy | Where-Object {$_.VolumeName -eq $HDDriveID} | Sort-Object InstallDate | Select-Object -Last 1
# Then mount it:
New-PSDrive -Name Y -PSProvider FileSystem -Root ($LastShadowCopy.DeviceObject + "\")

Works perfectly. Again, behavior is consistent with previous: once I reference (and map to drive letter) specific Shadow Copy with the code above, I can again use the form "\127.0.0.1\E$\@GMT-2018.06.27-05.00.09\". This doesn't matter anyway, tho, because once I have the Shadow Copy mapped to a drive letter, I can obviously access content via this drive letter.

Anyway, I'm happy with the solution. Although the question has been asked and answered I thought it might help somebody with the same problem if I don't just link to existing question.