DOCUMENT:Q103102  20-AUG-1993  [W_NT]
TITLE   :Repartitioning Corrupts Partition Table
PRODUCT :Windows NT
PROD/VER:3.10
OPER/SYS:WINDOWS
KEYWORDS:

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The information in this article applies to:
 
 - Microsoft Windows NT operating system, version 3.1
 - Microsoft Windows NT Advanced Server, version 3.1
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Disk Administrator (and the FDisk engine it shares with Setup) lays
down partition table information on a disk based on that disk's
Cylinder-Head-Sector geometry. For SCSI disks, this geometry is
invented by the driver, rather than being an inherent property of the
disk. Windows NT follows a relatively standard method of using a
geometry that produces 1-Megabyte tracks. However, other systems (or
SCSI disks run with BIOS) can use different geometries.
 
When a disk with multiple partitions is taken from one system to
another system which uses a different geometry, repartitioning it with
Disk Administrator can cause the partition table to become corrupt.
This is because Disk Administrator aligns all partitions on track
boundaries based on the current disk geometry. If the partition table
entry for an existing partition is rewritten with a new starting
offset, the data on that partition becomes inaccessible.
 
This can be corrected by editing the partition table (with an MS-DOS
boot floppy and Norton Utilities for example) to set the partition
starting sector and length back to its original value. You can use the
BIOS Parameter Block (BPB) in sector zero of the physical volume to
determine the geometry, or you can fish around for sector zero of the
partition, which also contains a BIOS Parameter Block, to find the
starting sector offset.
 
Additional reference words: 3.10
KBCategory:
KBSubCategory: NTAP

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