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Does chkdsk /r for VHDs make sense?

Answered Does chkdsk /r for VHDs make sense?

  • Saturday, April 07, 2012 11:20 PM
     
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    Hello!

    I had a RAID corruption on Hyper-V Server 2008 R2.

    I'm going to mount several dynamically expanding VHDs on the host in order to run chkdsk against them.

    Does it make any sense to run

    chkdsk driveletter: /f /r /x

    rather than

    chkdsk driveletter: /f /x

    since the physical sector condition is managed by the RAID controller and the Hyper-V host!?

    Thank you!

    L.

     

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  • Sunday, April 08, 2012 12:51 AM
     
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    Hi asklucas, since you mention you're going to mount several VHD's to the storage I suggest better to check within the VHD itself. Apart from that you can find more information from below mention article written by Ben Armstrong (http://blogs.msdn.com/b/virtual_pc_guy/archive/2009/01/07/how-do-i-fix-a-corrupted-virtual-hard-disk.aspx)

    Thanks,
    Susantha


     
  • Monday, April 09, 2012 6:24 AM
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    Hi,
     
    You can run chkdsk.
     
    By the way, you can also check the following post.
     
     

    Vincent Hu

    TechNet Community Support

    • Marked As Answer by asklucas Tuesday, April 10, 2012 8:10 AM
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  • Tuesday, April 10, 2012 8:12 AM
     
     
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    Thank you for your help!

    It states:

    <quote>

    I would recommend that you run a full fledged chkdsk /r on the disk in case corruption is found.

    We can find corruption by running chkdsk <drive_letter> or check id the dirty bit is set using the command fsutil dirty query <drive_letter>.

    In case corruption is detected, I would recommend running a chkdsk /r. Why i would recommend this is simple, if chkdsk finds some files in lost clusters, it would attempt to recover them and would put them in a folder titled found.xxx where xxx=001,002 etc.

    </quote>
     
  • Tuesday, April 10, 2012 8:22 AM
     
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    Thank you!

    Virtual PC Guy doesn't explain , which chkdsk parameters to use, but it's a very interesting post!

    I ended up running
    chkdsk driveletter: /f /r /x
    on the VHDs mounted in the parent partition.

    I created a quick-and-dirty script for that purpose, it also defrags and compacts the VHDs.

    Only use it for emergencies, as it's quick-and-dirty and relies on the diskpart list volume command to query (only the first!) drive letter of the attached disk.

    '	Hyper-V VHD Maintenance Script
'	LPET
'	2012-04-09

Option Explicit

Dim path_file_VHDs
path_file_VHDs = Array( _
	"D:\VHDs\firstdisk.vhd", _
	"D:\VHDs\seconddisk.vhd", _
	"D:\VHDs\thirddisk.vhd" _
	)


Main


Sub Main

	Dim path_file_VHD
	For Each path_file_VHD In path_file_VHDs
		
		WScript.Echo( "==============================================================================")
		WScript.Echo( "Processing VHD:")
		WScript.Echo( path_file_VHD)
		WScript.Echo( ISO_date( Now()) & " " & ISO_time( Now()))
		WScript.Echo( "------------------------------------------------------------------------------")
		
		Dim attached_drive_letter
		attached_drive_letter = attach_VHD( path_file_VHD)
		check_VHD( attached_drive_letter)
		defrag_VHD( attached_drive_letter)
		detach_VHD( path_file_VHD)
		
		compact_VHD( path_file_VHD)
		
		attached_drive_letter = ""
		
	Next

End Sub


Function attach_VHD( vhd_path)
	WScript.Echo( "attach_VHD( " & vhd_path & ")")

	Dim oShell
	Dim oScriptExec
	Dim oStdOut
	Dim oStdIn
	Dim strElement
	Dim sOut
	Dim sLine

	Set oShell = CreateObject( "WScript.Shell")
	Set oScriptExec = oShell.Exec( "diskpart")
	Set oStdOut = oScriptExec.StdOut
	Set oStdIn = oScriptExec.StdIn

	oStdIn.write vbCrLf
	WScript.Echo "select vdisk file=" & vhd_path
	oStdIn.write "select vdisk file=" & vhd_path & vbCrLf
	WScript.Echo "attach vdisk"
	oStdIn.write "attach vdisk" & vbCrLf
	WScript.Sleep( 15000)
	WScript.Echo "list volume"
	oStdIn.write "list volume" & vbCrLf
	WScript.Echo "exit"
	oStdIn.write "exit" & vbCrLf

	Do While Not oScriptExec.StdOut.AtEndOfStream
		sLine = oScriptExec.StdOut.ReadLine
		WScript.Echo sLine
		If InStr( sLine, "Volume 5    ") Then
			sOut = Trim( Right( Left( sLine, 18), 5)) & ":"
		End If
	Loop

	WScript.Echo sOut

	oStdIn.close()

	attach_VHD = sOut

End Function


Function check_VHD( drive_letter)
	WScript.Echo( "check_VHD( " & drive_letter & ")")

	Dim oShell
	Dim oScriptExec

	Dim command_line
	command_line = "chkdsk.exe " & drive_letter & " /f /r /x"

	Set oShell = CreateObject( "WScript.Shell")
	Set oScriptExec = oShell.Exec( command_line)

	Do While Not oScriptExec.StdOut.AtEndOfStream
		WScript.Echo( oScriptExec.StdOut.ReadLine)
	Loop

End Function


Function defrag_VHD( drive_letter)
	WScript.Echo( "defrag_VHD( " & drive_letter & ")")

	Dim oShell
	Dim oScriptExec

	Dim command_line
	command_line = "defrag.exe " & drive_letter & " /h /u /v"

	Set oShell = CreateObject( "WScript.Shell")
	Set oScriptExec = oShell.Exec( command_line)

	Do While Not oScriptExec.StdOut.AtEndOfStream
		WScript.Echo( oScriptExec.StdOut.ReadLine)
	Loop

End Function


Function detach_VHD( vhd_path)
	WScript.Echo( "detach_VHD( " & vhd_path & ")")

	Dim oShell
	Dim oScriptExec
	Dim oStdOut
	Dim oStdIn
	Dim strElement
	Dim sOut
	Dim sLine

	Set oShell = CreateObject( "WScript.Shell")
	Set oScriptExec = oShell.Exec( "diskpart")
	Set oStdOut = oScriptExec.StdOut
	Set oStdIn = oScriptExec.StdIn

	oStdIn.write vbCrLf
	WScript.Echo "select vdisk file=" & vhd_path
	oStdIn.write "select vdisk file=" & vhd_path & vbCrLf
	WScript.Echo "detach vdisk"
	oStdIn.write "detach vdisk" & vbCrLf
	WScript.Echo "exit"
	oStdIn.write "exit" & vbCrLf

	Do While Not oScriptExec.StdOut.AtEndOfStream
		sLine = oScriptExec.StdOut.ReadLine
		WScript.Echo sLine
		If instr( sLine, "successfully") Then
			sOut = sLine & vbCrLf
		End If
	Loop

	WScript.Echo sOut

	oStdIn.close()

End Function


Function compact_VHD( VHDName)
	WScript.Echo( "compact_VHD( " & VHDName & ")")

	Dim HyperVServer
	Dim Msvm_ImageManagementService
	Dim Result
	Dim Job
	Dim InParam
	Dim OutParam
	Dim WMI_Service

	'Set Hyper-V Server as being local
	HyperVServer = "."

	'Get an instance of the WMI Service in the virtualization namespace.
	Set WMI_Service = GetObject( "winmgmts:\\" & HyperVServer & "\root\virtualization")

	'Get the Msvm_ImageManagementService object
	Set Msvm_ImageManagementService = WMI_Service.ExecQuery( "SELECT * FROM Msvm_ImageManagementService").ItemIndex(0)

	'Setup the input parameter list
	Set InParam = Msvm_ImageManagementService.Methods_( "CompactVirtualHardDisk").InParameters.SpawnInstance_()
	InParam.Path = VHDName

	'Execute the method and store the results in OutParam
	Set OutParam = Msvm_ImageManagementService.ExecMethod_( "CompactVirtualHardDisk", InParam)

	'Check to see If the job completed synchronously
	If( OutParam.ReturnValue = 0 ) Then
		Wscript.Echo "The virtual hard disk has been compacted."
	ElseIf( OutParam.ReturnValue <> 4096 ) Then
		Wscript.Echo "The virtual hard disk has not been compacted."
	Else
		'Get the job object
		Set Job = WMI_Service.Get( OutParam.Job)
		'Wait for the job to complete (3 == starting, 4 == running)
		While ( Job.JobState = 3 ) Or ( Job.JobState = 4 )
			Wscript.Echo "Compacting. " & Job.PercentComplete & " % complete"
			WScript.Sleep( 20000)
			'Refresh the job object
			Set Job = WMI_Service.Get( OutParam.Job)
		Wend
		'Provide details If the job fails (7 == complete)
		If( Job.JobState <> 7 ) Then
			Wscript.Echo "The virtual hard disk has not been compacted."
			Wscript.Echo "ErrorCode: " & Job.ErrorCode
			Wscript.Echo "ErrorDescription: " & Job.ErrorDescription
		Else
			Wscript.Echo "The virtual hard disk has been compacted."
		End If
	End If

End Function


Function ISO_date( strNow)

	Dim strDD, strMM, strYYYY
	
	strYYYY = DatePart( "yyyy", strNow)
	strMM = Right( "0" & DatePart( "m", strNow), 2)
	strDD = Right( "0" & DatePart( "d", strNow), 2)
	
	ISO_date = strYYYY & "-" & strMM & "-" & strDD

End Function


Function ISO_time( strNow)

	ISO_time = Right( "0" & Hour( strNow), 2) & ":" & Right( "0" & Minute( strNow), 2) & ":" & Right( "0" & Second( strNow), 2)

End Function


     
  • Tuesday, April 10, 2012 8:24 AM
     
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    You  have to change the volume number depending on how many other (physical) disks are attached to the parent partition:

    	Do While Not oScriptExec.StdOut.AtEndOfStream
		sLine = oScriptExec.StdOut.ReadLine
		WScript.Echo sLine
		If InStr( sLine, "Volume 5    ") Then
			sOut = Trim( Right( Left( sLine, 18), 5)) & ":"
		End If
	Loop