dd'ing a Win2K drive - Should this work?

bscott at ntisys.com bscott at ntisys.com
Tue May 6 20:27:16 EDT 2003


On Tue, 6 May 2003, at 3:20pm, jason at sigio.com wrote:
> Win2K doesn't like to boot unless its on the first BIOS drive.

  Clarification: NTLDR [1] needs to be on the first INT 0x13 fixed disk
(disk 0x80).  Additionally, it must be in the active, primary partition.  
Microsoft calls this the "system drive" (with their usual ambiguousness with
regards to the physical-device/partition distinction).  If these conditions
are not met, Weird Things Can Happen.

  The partition containing the "system root" (usually \WINNT or \WINDOWS)  
can be anywhere NTLDR can reach.  Microsoft calls this the "boot drive".  
(Yes, I think that's backwards, too.  Complain to Microsoft.)  Note that
Microsoft (let alone anyone else) isn't always consistent in following this
terminology, either.

  If the drive letter of the "boot drive" changes, the system will break.  
There are references to this drive letter all over the system.  It does not
have to be C:, but it cannot change after install.  Drive letter assignment
under MS-Windows is arcane, but changing ordinal drive order [2], or
changing the absolute drive ID [3], will often cause the "boot drive" letter
to change.

  NTLDR does not know or care about drive letters.  It uses ordinal device
and partition numbers.  If the BIOS drive configuration changes, these will
change, and you will likely get boot failures.

  Getting back to the original post: A sector-by-sector copy will not, in
and of itself, be noticed or cause problems for MS-Windows.  The disk you
are copying to must be at least as large as the disk you copy from.

  If the disks are on different controllers, or will be moved between
controllers, then you must beware of geometry translation differences.  
Geometry translation is the process of producing artificial
cylinder/head/sector addresses for use with INT 0x13.  Two controllers may
use different methods, and/or the operating system may detect the method in
use incorrectly.  I have never found a completely satisfactory explanation
of exactly what happens here, but I do know that a geometry mismatch will
scramble your disk right quick.

  If you do a sector-by-sector copy, you cannot then place both physical
disks in the same Windows NT [4] system at the same time.  Windows NT puts a
unique ID (called a "SID") on any disk it sees.  A sector-by-sector copy
will copy that ID.  If both disks are then seen at once, Bad Things Happen.  
Microsoft provides a tool to fix this, called "SYSPREP".

  Any of the above could have contributed to the problem described in the
OP.  Given Paul's later comments, I would hesitate to make any guesses
without further investigation of the system by someone with more
multi-platform experience.


Footnotes
---------
[1] NTLDR = Windows NT Loader.  Kind of like "LILO".
[2] ordinal drive order = first disk, second disk, etc.
[3] absolute drive ID = unit ID for SCSI; channel and master/slave for IDE
[4] Windows 2000 = NT 5.0   Windows XP = NT 5.1

-- 
Ben Scott <bscott at ntisys.com>
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