Tierd storage spaces powershell path limit (Windows 10)

While working on my Set-StaticTier.ps1-script (will post a link later) I run into a strange 213 character path limit for the powershell commands Set-FileStorageTier and Clear-FileStorageTier on Windows 10 (1909).

First, lets try to create a folder with a 260 character name:

$Folder = "12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"
$Folder.Length
New-Item -ItemType Directory -Path h: -Name $Folder

(I don't know why the HTML-generator make a red box around : )
This will result in "260" followed by this error:

New-Item : The specified path, file name, or both are too long. The fully qualified file name must be less than 260 characters, and the directory name must be less than 248 characters.
At line:1 char:1
+ New-Item -ItemType Directory -Path h: -Name $Folder
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : WriteError: (H:\123456789012...678901234567890:String) [New-Item], PathTooLongException

    + FullyQualifiedErrorId : CreateDirectoryIOError,Microsoft.PowerShell.Commands.NewItemCommand

Ok, we now know that the full path must be shortar than 260 characters.


Lets try again with 213 characters in the full path, that is below the path limit.

First we set the variable for the folder name, and then measure how many characters we got.

$Folder = "12345678901234567890123456789012345678901234567189012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456790123456789012345"
$Folder.Length

This will result in "185".

Then we do the same for for the file.

$File = "12345678901234567890.txt"
$File.Length

This will result in "24".

If we add the  characters needed for the full path, drive letter + :\ is 3, and we need a backslash between the folder and file, that sums 4.

4 + $Folder.Length + $File.Length

This will result in "213".

Lets create the test-folder and file

New-Item -ItemType Directory -Path h: -Name $Folder
New-Item -ItemType File -Path "H:\$Folder" -Name $File
$FileToSet = (Get-ChildItem -Path h:\$Folder).FullName
$FileToSet.Length

This will result in "213". Good, then we did a proper calculation.

Now lets try the powershell commands to set/clear DesirerStorageTierClass:

Test-Path $FileToSet
Set-FileStorageTier -FilePath $FileToSet -DesiredStorageTierClass Capacity
Clear-FileStorageTier -FilePath $FileToSet

We run the Test-Path just to make sure that the path exists to remove that to our problems. Since we only have 212 characters in the path, we got no errors.

Lets do this all over, but we'll add a character to our file name.

$File = "123456789012345678901.txt"
$File.Length

This will result in "25".

After we create the folder and file we check the path length again:

$FileToSet.Length

This will result in "214".

Now lets try the powershell commands to set/clear DesirerStorageTierClass:

Test-Path $FileToSet

First we get a "True" from the Test-path, nothing wrong there.

Now lets run the Set-FileStorageTier command:

Set-FileStorageTier -FilePath $FileToSet -DesiredStorageTierClass Capacity

This results in an error:

Set-FileStorageTier : Invalid Parameter
Activity ID: {284aa8c7-35f3-460f-9980-6897ad86f43d}
At line:1 char:1
+ Set-FileStorageTier -FilePath $FileToSet -DesiredStorageTierClass Cap ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (StorageWMI:ROOT/Microsoft/...FileStorageTier) [Set-FileStorageTier], CimException
    + FullyQualifiedErrorId : StorageWMI 5,Set-FileStorageTier

Clear-FileStorageTier -FilePath $FileToSet

This also results in an error:

Clear-FileStorageTier : Invalid Parameter Activity ID: {ff02b437-b439-4952-a271-a8dff5c6be13} At line:1 char:1 + Clear-FileStorageTier -FilePath $FileToSet + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidArgument: (StorageWMI:ROOT/Microsoft/...FileStorageTier) [Clear-FileStorageTier], CimException + FullyQualifiedErrorId : StorageWMI 5,Clear-FileStorageTier


What have we learned from this?

The commands to set or clear a file to a desired storage tier class does not support file paths longer than 213 characters. Why is this? I have no idea!
I've search for some documentation regarding storage spaces maximum path lenghts but cannot find anything that says there is a different length limit while using a tierd storage space virtual disk.

If anyone uses tiered storage spaces virtual disks on a Windows Server-version, it would be very interesting to know if the same limit applies to the server version as on Windows 10.