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DataSource - USN journal log relationship RRS feed

  • Question

  • Colleagues!

    I'm curious 1) whether USN journal log file exists per datasource or not?

    2) Where is it stored?

    Thanks in advance!

    Nickolay 

    Friday, December 17, 2010 12:24 PM

Answers

  • Hi,

    The USN Journal is a feature of the NTFS file system.  It is enabled when you protect files or shares on a volume.  There is one journal per NTFS volume under protection.  You can get details about the USN journal (if one is enabled) by running:

     

    fsutil usn queryjournal c:   (where c: is the drive letter of the volume to query)


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Friday, December 17, 2010 10:24 PM
    Moderator
  • It is a internal file stored under \$Extend\$UsnJrnl:$J of the volume.
    ($Extend is directory under root of the volume, $UsnJrnl is filename and $J is alternate data stream on the file).

    and not accessible directly to any user mode applications (including dir/cmd etc).

    Also, the file is created as sparse and doesn't consume space until you really fill it up with metadata changes.

    Also note that, the USN is created by DPM (2007 and 2010) only for File System Protection (and shares) but not for applications like Exchange and Sql protection.

     

    Friday, December 24, 2010 10:37 AM
  • Hi,

     

    The USN Journal is only created and used on the protected servers volumes you are proetcting, It is not created or used on the DPM server, so you really cannot count it towards used disk space on the DPM server.   Also the USN journal file is a cyclic file, meaning it will wrap and not grow beyond the default size unless you manully grow it.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Monday, December 27, 2010 3:33 PM
    Moderator

All replies

  • Hi,

    The USN Journal is a feature of the NTFS file system.  It is enabled when you protect files or shares on a volume.  There is one journal per NTFS volume under protection.  You can get details about the USN journal (if one is enabled) by running:

     

    fsutil usn queryjournal c:   (where c: is the drive letter of the volume to query)


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Friday, December 17, 2010 10:24 PM
    Moderator
  • Thank you, Mike!
    Monday, December 20, 2010 11:40 AM
  • I can get the USN journal log size through DataSource property using PowerShell:

    $datasource.usnjournallogsize

    It usually equals 300MB but I cannot feel these MBs using disk properties window or diskmgmt.msc.

    Is it internal file?

    Nickolay

    Thursday, December 23, 2010 5:06 PM
  • It is a internal file stored under \$Extend\$UsnJrnl:$J of the volume.
    ($Extend is directory under root of the volume, $UsnJrnl is filename and $J is alternate data stream on the file).

    and not accessible directly to any user mode applications (including dir/cmd etc).

    Also, the file is created as sparse and doesn't consume space until you really fill it up with metadata changes.

    Also note that, the USN is created by DPM (2007 and 2010) only for File System Protection (and shares) but not for applications like Exchange and Sql protection.

     

    Friday, December 24, 2010 10:37 AM
  • Thank you, Arun!

    Very clear answer.

    Let me ask the last question in this topic:

    consider I'm trying to create my own report that contains data about how much space is occupied by particular datasource.

    Here I should take into account: disk and tape space datasource used.

    Disk Space = Replica Vol. Size + RecPoint Vol. Size

    The question: have I take into the account USN journal log size (that is datasource object property in DPM powershell snap-in) when I calculate datasource space occupied?

    Nickolay

    Friday, December 24, 2010 12:11 PM
  • Hi,

     

    The USN Journal is only created and used on the protected servers volumes you are proetcting, It is not created or used on the DPM server, so you really cannot count it towards used disk space on the DPM server.   Also the USN journal file is a cyclic file, meaning it will wrap and not grow beyond the default size unless you manully grow it.


    Regards, Mike J. [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Monday, December 27, 2010 3:33 PM
    Moderator