Changing an Azure VM Temp Drive to T:

Question

Changing an Azure VM Temp Drive to T:

David Downing 706

I need to move the Azure VM Temp Disk Drive from D: to another letter (probably T:). Because all of my provisioning setup and configuration are fully automated, I need to do this using a PowerShell script/commands.

Does anyone have a script or the commands necessary to move the temp drive from D: to another letter drive?

From several different queries, it seems like two reboots may be necessary. I did find another post that seems to indicate it's not required.

Because this automation will be used for a long time going forward, I want to do it correctly.

The VMs will be running Windows Server 2019 datacenter.

The new temp disk is already initialized and assigned to the T: drive.

Thank you,
David

kobulloc-MSFT 26,846 Reputation points Microsoft Employee Moderator

2021-12-01T08:38:07.793+00:00

@David Downing , manually changing drive letters on a VM is pretty straightforward, but I'm not sure there are any additional tools using ARM, Azure CLI, or Azure PowerShell (I'm still looking into this). There are PowerShell scripts out there that will do this:

https://devblogs.microsoft.com/powershell-community/changing-drive-letters-and-labels-via-powershell/#changing-drive-letter

Let me know if you need something different and I can do some additional digging (and if not, let me know as well so we can change this to an answer).
David Downing 706 Reputation points

2021-12-01T17:34:12.97+00:00

Thank you for the response!

I have a follow on question; if I change the D: drive to T: will the OS know the temp drive letter (with pagefile.sys) has been changed? If not, what is necessary to inform the OS of the change?
David Downing 706 Reputation points

2021-12-01T19:16:10.197+00:00

FYI... I tried the following:

$Drive = Get-CimInstance -ClassName Win32_Volume -Filter "DriveLetter = 'D:'"
$Drive | Set-CimInstance -Property @{DriveLetter ='T:'}

This is apparently not valid for the OS Temp Drive
kobulloc-MSFT 26,846 Reputation points Microsoft Employee Moderator

2021-12-01T20:15:26.3+00:00

@David Downing , Thank you for the heads up! I'll get a repro running and we'll see what the blocker is for the temp drive.
David Downing 706 Reputation points

2021-12-06T17:33:06.943+00:00

Hello,

Not sure, but the OS may also need to be notified that the PageFile.sys is moving to the T: drive.

Let me know if you need further clarification.

Thank you!

Answer accepted by question author

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kobulloc-MSFT 26,846 Reputation points Microsoft Employee Moderator

2021-12-01T08:38:07.793+00:00

@David Downing , manually changing drive letters on a VM is pretty straightforward, but I'm not sure there are any additional tools using ARM, Azure CLI, or Azure PowerShell (I'm still looking into this). There are PowerShell scripts out there that will do this:

https://devblogs.microsoft.com/powershell-community/changing-drive-letters-and-labels-via-powershell/#changing-drive-letter

Let me know if you need something different and I can do some additional digging (and if not, let me know as well so we can change this to an answer).
David Downing 706 Reputation points

2021-12-01T17:34:12.97+00:00

Thank you for the response!

I have a follow on question; if I change the D: drive to T: will the OS know the temp drive letter (with pagefile.sys) has been changed? If not, what is necessary to inform the OS of the change?
David Downing 706 Reputation points

2021-12-01T19:16:10.197+00:00

FYI... I tried the following:

$Drive = Get-CimInstance -ClassName Win32_Volume -Filter "DriveLetter = 'D:'"
$Drive | Set-CimInstance -Property @{DriveLetter ='T:'}

This is apparently not valid for the OS Temp Drive
kobulloc-MSFT 26,846 Reputation points Microsoft Employee Moderator

2021-12-01T20:15:26.3+00:00

@David Downing , Thank you for the heads up! I'll get a repro running and we'll see what the blocker is for the temp drive.
David Downing 706 Reputation points

2021-12-06T17:33:06.943+00:00

Hello,

Not sure, but the OS may also need to be notified that the PageFile.sys is moving to the T: drive.

Let me know if you need further clarification.

Thank you!

Answer 1

kobulloc-MSFT 26,846 Microsoft Employee Moderator

Hello, @David Downing !

Changing a drive letter both manually and with a PowerShell script
Thank you for being patient! I tried manually changing the Temporary Storage drive letter but ran into a "Parameter is incorrect" error. This was because I skipped over the prerequisite step of temporarily moving pagefile.sys to C drive like you mentioned. Once I did that, I was able to change the drive letter from D to T successfully both manually and using the PowerShell script:

$Drive = Get-CimInstance -ClassName Win32_Volume -Filter "DriveLetter = 'D:'"  
$Drive | Set-CimInstance -Property @{DriveLetter ='T:'}

One of the simplest approaches to scripting pagefile.sys would be:

wmic computersystem set AutomaticManagedPagefile=False

Once that has been completed, restart the VM and the script above to change the temp drive letter will run successfully. @David Downing (thank you!) has used the following to move the pagefile.sys to the temp drive:

wmic pagefileset where name="C:\pagefile.sys" delete  
wmic pagefileset create name="T:\pagefile.sys"  
wmic pagefileset where name="T:\pagefile.sys" set InitialSize=6144,MaximumSize=6144

Additional pagefile.sys options:

David Downing 706 Reputation points

2021-12-08T04:16:32.34+00:00

Thank you so much for the follow up! Please let me know if you're able to use PowerShell to move the Pagefile.sys from D: to C: then from C: to T:

I'll also continue trying... if successful, I'll post the answer here.
kobulloc-MSFT 26,846 Reputation points Microsoft Employee Moderator

2021-12-11T02:08:58.08+00:00
@David Downing ,

I was able to get the script to work by adding the following to the PowerShell script (and updated the original answer):

wmic computersystem set AutomaticManagedPagefile=False

(Restart VM)

$Drive = Get-CimInstance -ClassName Win32_Volume -Filter "DriveLetter = 'D:'" $Drive | Set-CimInstance -Property @{DriveLetter ='T:'}

You can also set automatic managed pagefile to true:

wmic computersystem set AutomaticManagedPagefile=True

I did some light experimentation and everything seemed to work as expected on the temp drive (now T). I hope that works for you!
David Downing 706 Reputation points

2021-12-14T04:25:44.223+00:00

I'm running a test now... just curious; how does the OS know the pagefile.sys is now on T: drive?

THX

Answer 2

David Downing 31

After running the test, I noticed the pagefile.sys no longer existed on any of the drives. To complete the move I ran the following and rebooted the computer.

wmic computersystem set AutomaticManagedPagefile=False
wmic pagefileset where name="C:\pagefile.sys" delete
wmic pagefileset create name="T:\pagefile.sys"
wmic pagefileset where name="T:\pagefile.sys" set InitialSize=6144,MaximumSize=6144

kobulloc-MSFT 26,846 Reputation points Microsoft Employee Moderator

2021-12-15T04:51:40.697+00:00

@David Downing , thank you for updating the thread with your results (and sorry you beat me to it). I'll update the other answer with what you've added here. Thank you!

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Changing an Azure VM Temp Drive to T:

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