Hey
I do have a NAS (from Hitachi) where I started to suffering about the slow writings. Single line into the text file could take seconds to get completed. After some troubleshooting efforts I found a way to test this in more control way.

If I run the command:
1..3000 | % { Add-Content -Value "abcdefghijklmn0123456" -Path x:\temp\DebugSlow.txt; Start-Sleep -Milliseconds 300 }

And then on another PS session do:
1..20 | % { $time = Measure-Command -Expression { Get-ChildItem x:\temp\d* }; write-host "$($time.seconds)s $($time.Milliseconds)ms" ; Start-Sleep -Seconds 1 }

I was able to get times like:

0s 157ms
0s 171ms
43s 384ms
3s 855ms
1s 223ms
1s 680ms

Add-content is the method what I have been using. But then I tested alternatives:
1..3000 | % { "abcdefghijklmn0123456" | Out-File -Path x:\temp\DebugSlow.txt; Start-Sleep -Milliseconds 300 }
And
1..3000 | % {Remove-Item -Path x:\temp\DebugSlow.txt ; Add-Content -Value "abcdefghijklmn0123456" -Path x:\temp\DebugSlow.txt; Start-Sleep -Milliseconds 300 }

I found out that with these, there were no slowness on the get-childitem.

I have also tested this with windows share as well, and that did not had similar slowness.

The “remove-item” test came from my colleague, as he thought this could have something to do with the seek till EOF on the add-content. If I delete the file, then there is no seek required.

To get better understanding how the PS is working, I would like to ask if anybody in here might know what might be causing the slowness on the add-content when accessing UNC share on NAS?