Compete PC Backup and wbadmin

Discussion in 'Windows Vista Performance' started by Tim, Jan 24, 2007.

  1. Tim

    Tim Guest

    I'm going to be using wbadmin to do backups so they can be done on a
    schedule. With Complete PC Backup, if there is already a backup file
    present, you are presented with following dialog:

    "The backup could take up to 157 GB of disk space. Because a previous
    backup already exists, all of this space might not be required, and only the
    differences will be saved. If there is not enough space on the disk, one or
    more of the older backups will be discarded starting with the oldest."

    Does wbadmin do the same thing? Are subsequent backups differential only?
    I see no command line switch to set this one way or the other. Also, will
    wbadmin automatically delete older backups to free up disk space? Thanks
    for any help.
    Tim, Jan 24, 2007
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  2. Jill Zoeller [MSFT], Jan 24, 2007
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  3. Tim

    Tim Guest

    Thanks for the link. While we're on this subject, I have some other
    questions since I know little about shadow copies. My understanding is that
    the first backup file is a .vhd file, and subsequent differential backups
    are shadow copies. If, for example, the only change in the volume is the
    deletion of one file, what gets stored in the shadow copy? Is it just an
    indicator that the file has been deleted? Does this take up space? Say,
    for example that the only change is one file being added. Will the shadow
    copy only contain this one file? If that file is later deleted, will that
    shadow copy also be deleted? If I perform a backup every day, is the shadow
    copy composed of the difference between today's configuration and the
    original .vhd file, or today's configuration and the original .vhd file plus
    all subsequent shadow copies? I guess my concern here is that the totality
    of the backups will eventually be much larger than the current drive being
    backed up. Is this the way it works? Thanks.
    Tim, Jan 25, 2007
  4. Hi Tim,
    To answer your questions:
    Nothing changes until the blocks previously occupied by the file are
    In general, every block level change on the volume will consume space on the
    shadow copy storage area. But file deletions by them selved don't amount to

    Is it just an
    The last statement could be true depending on how many shadow copies you
    keep and your usage patterns. If you backed up and then overwrote your
    entire volume and backed up again, you would consume twice the space.

    We have a slide presentation somewhere that illustrates this. If I find it,
    I can email it to you. I don't think it's NDA.

    This posting is provided "AS IS" with no warranties, and confers no rights.

    Want to learn more about Windows file and storage technologies? Visit our
    team blog at
    Jill Zoeller [MSFT], Jan 26, 2007
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