What gets put in an MBR other than the Partition Table?

Discussion in 'Acronis Disk Director Suite' started by Howard Kaikow, Jul 30, 2009.

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  1. Howard Kaikow

    Howard Kaikow Registered Member

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    When ADD modifies the partitions on a drive, does anything in the MBR, other than the Partition Table, get modified?

    In particular is anything modified in the boot sector, i.e., the first 446 bytes of the MBR?
     
  2. K0LO

    K0LO Registered Member

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    Howard:

    No, it should not modify anything in the first sector other than some of the bytes in the 64-byte partition table.

    You could copy the first sector of your disk to a file (file #1) then modify the partitions with DD, then again copy the first sector to a file (file #2). Compare file #1 with file #2 to find out which bytes are modified.

    If I had a few extra minutes I'd do this in a VM to demonstrate. Unfortunately, work beckons...
     
  3. Howard Kaikow

    Howard Kaikow Registered Member

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    I'll do that.

    A few daze ago, I used Recovery Console to clean up the MBR on each of 4 drives. Hopefully, there's no Partition Magic crap left behind.
     
  4. Howard Kaikow

    Howard Kaikow Registered Member

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    What do you use to copy the first sector?

    I do so by booting to Ubuntu and copying there.
    Is there a way to do this in Windows?
     
  5. K0LO

    K0LO Registered Member

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    You can use Disk Director to do this. Use the Disk Editor to view the first sector. Highlight all of the bytes in the first sector and save it to a file on your disk.

    The disk editor is also handy for comparing two sectors. If you copy the saved file to a blank sector on your disk and then copy the second file on top of the first, the differences will be shown in color. The blank sectors between 2 and 62 are handy for this purpose. You can write zeros back to them when finished.
     
  6. MudCrab

    MudCrab Imaging Specialist

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    You can use the Disk Editor in DD to save Sector 0 to a file. Once saved, you can then read the file back in. Changes will be a different color (I think green) so you can easily see what's been changed. Don't commit the changes (save the sector) if you want to leave it like it is.
     
  7. K0LO

    K0LO Registered Member

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    Howard:

    Here is an example from Virtual XP. The following two pictures are the virtual disk layout before and after adding a partition:

    MBR 2.PNG
    MBR 3.PNG

    This is the first sector on the disk before adding the new partition:

    MBR 1.PNG

    And this is the first sector after adding the new partition. The changed bytes are in green:

    MBR 4.PNG

    As you can see, only the third slot of the partition table was modified. None of the other bytes changed.
     
  8. Howard Kaikow

    Howard Kaikow Registered Member

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    I'm just about convinced that the problem causing slower performance of Ubuntu 9.04 vs Ubuntu 7.04 is not the swap partion's location.

    I believe that it is the generic video driver used for the Radeon card.

    Using System Monitor in Ubuntu shows that the swap partition is not even being used, and there is plenty of unused memory, but screen updatunfg is veeeery slow.

    I'll go to Radeon's web site and see what drivers they have.
     
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