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File Backups to External Drive - What if Delete Files on WHS? RRS feed

  • Question

  • I have an external USB drive of 2TB I am using to backup files from my WHS. How do these backups work? Will they overwrite existing files if they've changed? And what if I delete a file from the WHS, will that file be deleted from the backup next time I go to backup?
    Monday, August 3, 2009 4:17 AM

Answers

  • Hello Mark,
    The backup is incremental in respect to disk usages but always creates a new sub directory on your USB drive with all files. The sub directories name contains date and time, so you can very easily identify the latest backup. In each sub directory you will find a copy of all new or changed files together with the files already backup up. This is done by creating hard links to the existing files. These files simply have two or more names and show up in each sub directory of the backup.

    To answer your questions:
    A changed file is copied again into the current backup. Previous version do still exist in previous backups.
    A deleted file is no longer in the current backup but will still exist in any previous backup.

    Martin
    LightsOut - Power Management for Windows Home Server http://www.home-server-blog.de/add-ins/lightsout/#en
    • Proposed as answer by kariya21Moderator Tuesday, August 4, 2009 2:08 AM
    • Marked as answer by MarkBx Thursday, August 6, 2009 2:32 AM
    Monday, August 3, 2009 7:11 AM
    Moderator
  • ...
    If I delete (1) then all data from (2) and (3) remain intact?
    ...
    That's correct. A hard link is an NTFS "pointer" to the actual data. Only when all pointers to the data are deleted will the data itself be deleted.
    I'm not on the WHS team, I just post a lot. :)
    • Proposed as answer by kariya21Moderator Tuesday, August 4, 2009 2:08 AM
    • Marked as answer by MarkBx Thursday, August 6, 2009 2:32 AM
    Monday, August 3, 2009 5:48 PM
    Moderator

All replies

  • Hello Mark,
    The backup is incremental in respect to disk usages but always creates a new sub directory on your USB drive with all files. The sub directories name contains date and time, so you can very easily identify the latest backup. In each sub directory you will find a copy of all new or changed files together with the files already backup up. This is done by creating hard links to the existing files. These files simply have two or more names and show up in each sub directory of the backup.

    To answer your questions:
    A changed file is copied again into the current backup. Previous version do still exist in previous backups.
    A deleted file is no longer in the current backup but will still exist in any previous backup.

    Martin
    LightsOut - Power Management for Windows Home Server http://www.home-server-blog.de/add-ins/lightsout/#en
    • Proposed as answer by kariya21Moderator Tuesday, August 4, 2009 2:08 AM
    • Marked as answer by MarkBx Thursday, August 6, 2009 2:32 AM
    Monday, August 3, 2009 7:11 AM
    Moderator
  • Thanks. So I if I delete my original backup after backing up two or three times since then, it will maintain all the data as it was backed up on that date? Just so I'm clear what I'm asking, here's an example:

    (1) Initial Backup 7/30/09
    (2) Backup 7/31/09
    (3) Backup 8/2/09

    If I delete (1) then all data from (2) and (3) remain intact?

    I ask this because doing these additional backups, the total file size on the drive only increased 1 or 2 MB, which is probably only what changed.

    BTW - I'll have to give your "lightsout" add-on a try. Looks quite useful!
    Monday, August 3, 2009 3:55 PM
  • ...
    If I delete (1) then all data from (2) and (3) remain intact?
    ...
    That's correct. A hard link is an NTFS "pointer" to the actual data. Only when all pointers to the data are deleted will the data itself be deleted.
    I'm not on the WHS team, I just post a lot. :)
    • Proposed as answer by kariya21Moderator Tuesday, August 4, 2009 2:08 AM
    • Marked as answer by MarkBx Thursday, August 6, 2009 2:32 AM
    Monday, August 3, 2009 5:48 PM
    Moderator