Block level Reading of files on a system and backup them

Discussion in 'C' started by vrushali662, Feb 3, 2011.

  1. vrushali662

    vrushali662 New Member

    Joined:
    Feb 3, 2011
    Messages:
    3
    Likes Received:
    0
    Trophy Points:
    0
    Occupation:
    sgsd
    Location:
    gfsdg
    Can anybody help with different approaches identifying modified disk blocks in a filesystem? Finding out a way to get list of modified blocks on filesystem and backup them?
     
  2. xpi0t0s

    xpi0t0s Mentor

    Joined:
    Aug 6, 2004
    Messages:
    3,009
    Likes Received:
    203
    Trophy Points:
    63
    Occupation:
    Senior Support Engineer
    Location:
    England
    To determine if a block has been modified you need some record of its previous contents. The most accurate way of doing this is with a simple block copy, but of course that needs twice the disk space. For a smaller footprint you could summarise the block contents, for example with an MD5 checksum, but you can't map a large number onto a small number without some risk of duplication, for instance if the block contents change in such a way that the MD5 of both copies is identical, you wouldn't be able to determine that from the new and old MD5s.

    The other problem with a block-based backup is that this doesn't necessarily map well onto the filesystem. If the filesystem is reorganised without any files changing, for example with a defragger, then a block-based incremental backup won't be able to restore. Since users care about files, not blocks, it would be a better idea to perform a file-based backup than a block-based backup.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice