Windows file share: why sometimes newly created files aren’t visible for some period of time

server-message-blockwindows

Please note, I copied this question from SO, because understood that ServerFault is better place for such kind of questions (https://stackoverflow.com/questions/5159220)

Hello

We were faced with very strange issue that made us crazy. Sometimes newly created files on our File Share PC were "absent" for some period of time. To reproduce a problem you should have at least two computers, call them alpha and beta. Create file share on beta PC (\\beta\share\bug) and run this PowerShell script from alpha PC:

param(
  $sharePath="\\beta\share\bug"
)
$sharePC = ($sharePath -split '\\')[2]
$session = New-PSSession -ComputerName $sharePC
$counter = 0
while ($true) {
  $fileName = $sharePath + "\$counter.txt"
  Invoke-Command -Session $session -ScriptBlock {
    param(
      $fileName
    )
    "" > $fileName
  } -ArgumentList $fileName
  if (Test-Path $fileName) {
    Write-Host "File $fileName exists" -fore Green
  } else {
    Write-Host "!!! File $fileName does NOT exist!" -fore Red
  }

  $counter = $counter + 1
  Start-Sleep 2
}

After starting this script you should be able to see these messages:

File \\beta\share\bug\1.txt exists
File \\beta\share\bug\2.txt exists
...

And now:
Open cmd.exe and run this command:

if exist \\beta\share\bug\foo.txt echo 1

After this you'll during approx 10 seconds you'll see following messages:

!!! File \\beta\share\bug\3.txt does NOT exist!
!!! File \\beta\share\bug\4.txt does NOT exist!

We've discovered that bug is caused by enumerating shared directory where new files are being created. In Python call os.listdir('//beta/share/bug') to reproduce a bug. In C#: Directory.GetDirectories(@"\\beta\share\bug"). You can even simply navigate to share directory by shell and call ls or dir.

Bug were found on Windows Server 2008 R2. Bug also can be reproduced on Windows 7 (on both OSs SMB 2.0 is installed)

Note, that you cannot watch directory content on alpha PC in Windows Explorer in real time, because if you open this directory in Explorer bug would not occur! So ensure to close all such windows before attempts to reproduce a bug. After each script restart you should manually remove all already created files from share (because script is rather stupid and always starts from 0.txt).

We currently have 2 workarounds for this issue:

  1. If client sees this situation, it creates some temporary file in problematic directory – after this files magically appear.
  2. Disable SMB 2.0: http://www.petri.co.il/how-to-disable-smb-2-on-windows-vista-or-server-2008.htm

Does anybody have ever discovered similar problem and can explain why it occurs and how "correctly fix" it?

Thanks

Best Answer

Our current solution that just works: Disable SMB 2.0 (http://www.petri.co.il/how-to-disable-smb-2-on-windows-vista-or-server-2008.htm)

Related Topic