Resizing the MBR?

Discussion in 'Computer Support' started by cizzo, Jun 21, 2007.

  1. cizzo

    cizzo Guest

    Is it possible to expand the MBR?
    I want to expand the MBR from 32 sectors to 63
    cizzo, Jun 21, 2007
    #1
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  2. cizzo

    pcbutts1 Guest

    Why?


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    "cizzo" <> wrote in message
    news:...
    > Is it possible to expand the MBR?
    > I want to expand the MBR from 32 sectors to 63
    >
    pcbutts1, Jun 21, 2007
    #2
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  3. pcbutts1 wrote:
    > Why?


    It's for his boot manager, one that demands a certain amount of space to
    work. I'd go with something a little more reasonable.
    =?ISO-8859-1?Q?R=F4g=EAr?=, Jun 21, 2007
    #3
  4. cizzo

    Vanguard Guest

    "cizzo" <> wrote in message
    news:...
    > Is it possible to expand the MBR?
    > I want to expand the MBR from 32 sectors to 63
    >



    The MBR (master boot record) is only just 1 sector (512 bytes) in size.
    It will remain that size so the BIOS can read and find the 64-byte
    partition table (4 records at 16-bytes each for each partition),
    446-byte bootstrap code, and 2-byte disk signature. Because that sector
    is used for the MBR, it will never be included in any partition, and
    that means the rest of the first track also remains unusable (i.e., that
    track won't get added to any partition because its 1st sector is the MBR
    that must be outside any partition). A track is 63 sectors and each
    sector is 512 bytes, so the 62 sectors (after the sector for the MBR) in
    the rest of the unusable 1st track give the boot manager program another
    31,744 bytes to work with.

    Boot managers can, if coded to do so, use the 446-byte bootstrap area in
    the MBR which can then extend into the rest of the unusable first track.
    This is unlike some boot managers, like BootMagic, that requires a
    partition to hold the rest of its program code or, like Microsoft's
    dual-boot operation, uses the boot sector (the first one) in a partition
    to contain yet another bootstrap program. For example, GAG (at
    sourceforge.net) is 26KB in size so it won't fit within just the tiny
    446-byte bootstrap area of the MBR (1st sector of 1st track). However,
    rather than require the rest of its program to reside within a partition
    (which could disappear if you format or delete partitions), the rest of
    its program code goes into the unusable 1st track.

    I've heard something called System Commander does that, too, but I
    haven't used it so I can't verify that and I don't know if *all* of
    System Commander resides in the 446-byte bootstrap area of the MBR and
    within the rest of the sectors of the 1st unusable track.

    YOU will (or should) never change the size of the MBR. It is just 1
    sector in size. That's all the BIOS will read to get the partition
    info, bootstrap code, and disk signature (not used by the BIOS but used
    by the OS). Since you think your MBR is already 32 sectors in size, I
    don't know what you are really are asking about. MBR = 1 sector, will
    always be 1 sector, will always be the 1st sector on the first physical
    hard drive detected by the system BIOS (it is possible another BIOS,
    like for SATA or SCSI can select a different physical drive but the
    system BIOS would have to pass control to them).

    MBR = 1 sector
    Vanguard, Jun 22, 2007
    #4
  5. cizzo

    why? Guest

    On Thu, 21 Jun 2007 14:30:47 -0700, pcbutts1 wrote:

    >Why?


    What?

    Me
    why?, Jun 22, 2007
    #5
  6. cizzo

    cizzo Guest

    On Jun 21, 9:10 pm, "Vanguard" <> wrote:
    > "cizzo" <> wrote in message
    >
    > news:...
    >
    > > Is it possible to expand the MBR?
    > > I want to expand the MBR from 32 sectors to 63

    >
    > The MBR (master boot record) is only just 1 sector (512 bytes) in size.
    > It will remain that size so the BIOS can read and find the 64-byte
    > partition table (4 records at 16-bytes each for each partition),
    > 446-byte bootstrap code, and 2-byte disk signature. Because that sector
    > is used for the MBR, it will never be included in any partition, and
    > that means the rest of the first track also remains unusable (i.e., that
    > track won't get added to any partition because its 1st sector is the MBR
    > that must be outside any partition). A track is 63 sectors and each
    > sector is 512 bytes, so the 62 sectors (after the sector for the MBR) in
    > the rest of the unusable 1st track give the boot manager program another
    > 31,744 bytes to work with.
    >
    > Boot managers can, if coded to do so, use the 446-byte bootstrap area in
    > the MBR which can then extend into the rest of the unusable first track.
    > This is unlike some boot managers, like BootMagic, that requires a
    > partition to hold the rest of its program code or, like Microsoft's
    > dual-boot operation, uses the boot sector (the first one) in a partition
    > to contain yet another bootstrap program. For example, GAG (at
    > sourceforge.net) is 26KB in size so it won't fit within just the tiny
    > 446-byte bootstrap area of the MBR (1st sector of 1st track). However,
    > rather than require the rest of its program to reside within a partition
    > (which could disappear if you format or delete partitions), the rest of
    > its program code goes into the unusable 1st track.
    >
    > I've heard something called System Commander does that, too, but I
    > haven't used it so I can't verify that and I don't know if *all* of
    > System Commander resides in the 446-byte bootstrap area of the MBR and
    > within the rest of the sectors of the 1st unusable track.
    >
    > YOU will (or should) never change the size of the MBR. It is just 1
    > sector in size. That's all the BIOS will read to get the partition
    > info, bootstrap code, and disk signature (not used by the BIOS but used
    > by the OS). Since you think your MBR is already 32 sectors in size, I
    > don't know what you are really are asking about. MBR = 1 sector, will
    > always be 1 sector, will always be the 1st sector on the first physical
    > hard drive detected by the system BIOS (it is possible another BIOS,
    > like for SATA or SCSI can select a different physical drive but the
    > system BIOS would have to pass control to them).
    >
    > MBR = 1 sector


    What I want to expand is the size of the "free space" before the first
    primary partition from sector 32 to sector 63 (usually the first track/
    cylinder boundry) as indicated by several partitioning programs I have
    used on several hdds. Any reason to why some drives start at the 32nd
    sector and some at 63?
    cizzo, Jun 22, 2007
    #6
  7. cizzo

    Vanguard Guest

    "cizzo" <> wrote in message
    news:...
    > On Jun 21, 9:10 pm, "Vanguard" <> wrote:
    >> "cizzo" <> wrote in message
    >>
    >> news:...
    >>
    >> > Is it possible to expand the MBR?
    >> > I want to expand the MBR from 32 sectors to 63

    >>
    >> The MBR (master boot record) is only just 1 sector (512 bytes) in
    >> size.
    >> It will remain that size so the BIOS can read and find the 64-byte
    >> partition table (4 records at 16-bytes each for each partition),
    >> 446-byte bootstrap code, and 2-byte disk signature. Because that
    >> sector
    >> is used for the MBR, it will never be included in any partition, and
    >> that means the rest of the first track also remains unusable (i.e.,
    >> that
    >> track won't get added to any partition because its 1st sector is the
    >> MBR
    >> that must be outside any partition). A track is 63 sectors and each
    >> sector is 512 bytes, so the 62 sectors (after the sector for the MBR)
    >> in
    >> the rest of the unusable 1st track give the boot manager program
    >> another
    >> 31,744 bytes to work with.
    >>
    >> Boot managers can, if coded to do so, use the 446-byte bootstrap area
    >> in
    >> the MBR which can then extend into the rest of the unusable first
    >> track.
    >> This is unlike some boot managers, like BootMagic, that requires a
    >> partition to hold the rest of its program code or, like Microsoft's
    >> dual-boot operation, uses the boot sector (the first one) in a
    >> partition
    >> to contain yet another bootstrap program. For example, GAG (at
    >> sourceforge.net) is 26KB in size so it won't fit within just the tiny
    >> 446-byte bootstrap area of the MBR (1st sector of 1st track).
    >> However,
    >> rather than require the rest of its program to reside within a
    >> partition
    >> (which could disappear if you format or delete partitions), the rest
    >> of
    >> its program code goes into the unusable 1st track.
    >>
    >> I've heard something called System Commander does that, too, but I
    >> haven't used it so I can't verify that and I don't know if *all* of
    >> System Commander resides in the 446-byte bootstrap area of the MBR
    >> and
    >> within the rest of the sectors of the 1st unusable track.
    >>
    >> YOU will (or should) never change the size of the MBR. It is just 1
    >> sector in size. That's all the BIOS will read to get the partition
    >> info, bootstrap code, and disk signature (not used by the BIOS but
    >> used
    >> by the OS). Since you think your MBR is already 32 sectors in size,
    >> I
    >> don't know what you are really are asking about. MBR = 1 sector,
    >> will
    >> always be 1 sector, will always be the 1st sector on the first
    >> physical
    >> hard drive detected by the system BIOS (it is possible another BIOS,
    >> like for SATA or SCSI can select a different physical drive but the
    >> system BIOS would have to pass control to them).
    >>
    >> MBR = 1 sector

    >
    > What I want to expand is the size of the "free space" before the first
    > primary partition from sector 32 to sector 63 (usually the first
    > track/
    > cylinder boundry) as indicated by several partitioning programs I have
    > used on several hdds. Any reason to why some drives start at the 32nd
    > sector and some at 63?




    My guess is that you have the BIOS configured to use the old CHS scheme
    to map the cylinders, heads, and sectors on the hard drive rather than
    setting it to LBA (large block addressing) mode which simply uses a
    linear scaling of 0 to N sectors (counting for sectors starts at zero,
    not one). The BIOS does the geometric translation using the BIOS INT13
    extended calls to map from LBA mode (linear sector counting) to the CHS
    scheme (see http://www.pcguide.com/ref/hdd/bios/modes.htm; old but still
    valid info). I personally have not seen the second (first usable) track
    start at sector 33 for many years (but then I've probably defaulted or
    enabled LBA mode for over a decade).

    Which partition management utilities do you have? PartitionMagic maybe?
    If so, select the drive in PM and select Properties. Then look under
    the Properties dialog and under the Partition Info panel. What is the
    info listed there? And if using NTFS, what info is listed under the
    NTFS panel? If you don't have PM then the Ranish PartitionManager is
    free but I've not used it so I don't know what details it will show or
    where to navigate to them in the program.

    Are you using a disk overlay manager in the bootstrap area of the MBR to
    compensate for an old BIOS that doesn't support LBA mode or drives over
    132GB in size per partition?

    Are the rest of the tracks also only 32 sectors in size or is it just
    the first one? Was this on a SCSI drive, or a SATA drive (which is
    handled as a SCSI device? Their BIOS may permit varying the sizes from
    the defaults. SCSI already uses a linear scaling scheme like LBA but
    the format of the partition table is still the same (1 byte to denote
    active partition, 3 bytes for CHS start sector, 1 byte for partition
    type, 3 bytes for CHS end sector, 4 bytes for starting sector, 4 bytes
    for sector length).

    Some viruses work by shifting the partition table in the MBR to
    somewhere else (in the MBR or in the 1st track after the 1st sector) and
    usurp the bootstrap code in the MBR so the partition gets found - until
    they want to do their nasty action, like replace the bootstrap code with
    the standard loader program which won't know how to find the moved
    partition table so it looks like you lost all partitions on the drive.
    Using any whole-disk encryption programs (the use the MBR bootstrap area
    and might do similar to viruses regarding moving around the contents of
    the MBR and starting sectors and how many sectors in a track along with
    their encryption).

    What OS are you using? Windows? If so, FAT or NTFS partitions? Using
    Linux with its grub bootstrap loader? Linux will accept 2, or more,
    extended partitions in the MBR. OS/2 involved anywhere? It keeps a
    private copy of the partition table that can cause problems with 3rd
    party partition tools that expect standard sizes and default offsets for
    objects within the sectors.
    Vanguard, Jun 23, 2007
    #7
  8. cizzo

    cizzo Guest

    On Jun 22, 5:18 pm, "Vanguard" <> wrote:
    > "cizzo" <> wrote in message
    >
    > news:...
    >
    >
    >
    >
    >
    > > On Jun 21, 9:10 pm, "Vanguard" <> wrote:
    > >> "cizzo" <> wrote in message

    >
    > >>news:...

    >
    > >> > Is it possible to expand the MBR?
    > >> > I want to expand the MBR from 32 sectors to 63

    >
    > >> The MBR (master boot record) is only just 1 sector (512 bytes) in
    > >> size.
    > >> It will remain that size so the BIOS can read and find the 64-byte
    > >> partition table (4 records at 16-bytes each for each partition),
    > >> 446-byte bootstrap code, and 2-byte disk signature. Because that
    > >> sector
    > >> is used for the MBR, it will never be included in any partition, and
    > >> that means the rest of the first track also remains unusable (i.e.,
    > >> that
    > >> track won't get added to any partition because its 1st sector is the
    > >> MBR
    > >> that must be outside any partition). A track is 63 sectors and each
    > >> sector is 512 bytes, so the 62 sectors (after the sector for the MBR)
    > >> in
    > >> the rest of the unusable 1st track give the boot manager program
    > >> another
    > >> 31,744 bytes to work with.

    >
    > >> Boot managers can, if coded to do so, use the 446-byte bootstrap area
    > >> in
    > >> the MBR which can then extend into the rest of the unusable first
    > >> track.
    > >> This is unlike some boot managers, like BootMagic, that requires a
    > >> partition to hold the rest of its program code or, like Microsoft's
    > >> dual-boot operation, uses the boot sector (the first one) in a
    > >> partition
    > >> to contain yet another bootstrap program. For example, GAG (at
    > >> sourceforge.net) is 26KB in size so it won't fit within just the tiny
    > >> 446-byte bootstrap area of the MBR (1st sector of 1st track).
    > >> However,
    > >> rather than require the rest of its program to reside within a
    > >> partition
    > >> (which could disappear if you format or delete partitions), the rest
    > >> of
    > >> its program code goes into the unusable 1st track.

    >
    > >> I've heard something called System Commander does that, too, but I
    > >> haven't used it so I can't verify that and I don't know if *all* of
    > >> System Commander resides in the 446-byte bootstrap area of the MBR
    > >> and
    > >> within the rest of the sectors of the 1st unusable track.

    >
    > >> YOU will (or should) never change the size of the MBR. It is just 1
    > >> sector in size. That's all the BIOS will read to get the partition
    > >> info, bootstrap code, and disk signature (not used by the BIOS but
    > >> used
    > >> by the OS). Since you think your MBR is already 32 sectors in size,
    > >> I
    > >> don't know what you are really are asking about. MBR = 1 sector,
    > >> will
    > >> always be 1 sector, will always be the 1st sector on the first
    > >> physical
    > >> hard drive detected by the system BIOS (it is possible another BIOS,
    > >> like for SATA or SCSI can select a different physical drive but the
    > >> system BIOS would have to pass control to them).

    >
    > >> MBR = 1 sector

    >
    > > What I want to expand is the size of the "free space" before the first
    > > primary partition from sector 32 to sector 63 (usually the first
    > > track/
    > > cylinder boundry) as indicated by several partitioning programs I have
    > > used on several hdds. Any reason to why some drives start at the 32nd
    > > sector and some at 63?

    >
    > My guess is that you have the BIOS configured to use the old CHS scheme
    > to map the cylinders, heads, and sectors on the hard drive rather than
    > setting it to LBA (large block addressing) mode which simply uses a
    > linear scaling of 0 to N sectors (counting for sectors starts at zero,
    > not one). The BIOS does the geometric translation using the BIOS INT13
    > extended calls to map from LBA mode (linear sector counting) to the CHS
    > scheme (seehttp://www.pcguide.com/ref/hdd/bios/modes.htm;old but still
    > valid info). I personally have not seen the second (first usable) track
    > start at sector 33 for many years (but then I've probably defaulted or
    > enabled LBA mode for over a decade).


    There is no option in the BIOS for this.

    >
    > Which partition management utilities do you have? PartitionMagic maybe?
    > If so, select the drive in PM and select Properties. Then look under
    > the Properties dialog and under the Partition Info panel. What is the
    > info listed there? And if using NTFS, what info is listed under the
    > NTFS panel? If you don't have PM then the Ranish PartitionManager is
    > free but I've not used it so I don't know what details it will show or
    > where to navigate to them in the program.
    >


    It is using NTFS. It is saying the starting sector is 32 (I want it
    to start at 63)

    > Are you using a disk overlay manager in the bootstrap area of the MBR to
    > compensate for an old BIOS that doesn't support LBA mode or drives over
    > 132GB in size per partition?


    I am fairly certain we are not doing so.

    >
    > Are the rest of the tracks also only 32 sectors in size or is it just
    > the first one? Was this on a SCSI drive, or a SATA drive (which is
    > handled as a SCSI device? Their BIOS may permit varying the sizes from
    > the defaults. SCSI already uses a linear scaling scheme like LBA but
    > the format of the partition table is still the same (1 byte to denote
    > active partition, 3 bytes for CHS start sector, 1 byte for partition
    > type, 3 bytes for CHS end sector, 4 bytes for starting sector, 4 bytes
    > for sector length).
    >

    It does appear as if the rest of the tracks are 32 sectors in size
    (have to verify this)
    It is an SCSI drive running on a raid 1+0 array (it is a server)

    > Some viruses work by shifting the partition table in the MBR to
    > somewhere else (in the MBR or in the 1st track after the 1st sector) and
    > usurp the bootstrap code in the MBR so the partition gets found - until
    > they want to do their nasty action, like replace the bootstrap code with
    > the standard loader program which won't know how to find the moved
    > partition table so it looks like you lost all partitions on the drive.
    > Using any whole-disk encryption programs (the use the MBR bootstrap area
    > and might do similar to viruses regarding moving around the contents of
    > the MBR and starting sectors and how many sectors in a track along with
    > their encryption).


    Fairly certain there are no virus's on our system.

    >
    > What OS are you using? Windows? If so, FAT or NTFS partitions? Using
    > Linux with its grub bootstrap loader? Linux will accept 2, or more,
    > extended partitions in the MBR. OS/2 involved anywhere? It keeps a
    > private copy of the partition table that can cause problems with 3rd
    > party partition tools that expect standard sizes and default offsets for
    > objects within the sectors.- Hide quoted text -
    >


    We are running Windows Server 2003 Standard and Enterprise edition.

    Thank you for your questions, they have given me some things to think
    about. If you have further suggestions based on my replies I would
    greatly appreciate it.

    > - Show quoted text -
    cizzo, Jul 3, 2007
    #8
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