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Some people on the list wanted to have large boot partitions under Win NT.
This
article may help if they have problems with those large partitions.
Joe
Windows NTtm Technical Article
25 October 1999
Large Disk Boot Problems
References:
Microsoft Knowledge Base Article Q114841
Microsoft Knowledge Base Article Q127134
If your Windows NT boot partition is too large or it is not the first
partition on the hard disk, your computer may suddenly refuse to boot.
This article explains why this can happen, how to recover from it, and how
to prevent it in the first place.
What is Happening
Windows NT's NTFS disk format allows huge partitions. With a 512 byte
cluster size, you can format a partition of 2 terabytes (TB). That's two
trillion bytes, enough to hold about 4.5 million books. The maximum 64KB
cluster size allows 256TB, or well over half a billion books. But even
though Windows NT can address all of this huge space, the boot process
starts with your BIOS (Basic Input/Output System), not Windows NT.
The BIOS locates the beginning of a partition by using three numbers: The
Starting Side (or Head), the Starting Cylinder, and the Starting Sector.
The end of a partition is identified by three similar numbers. Now, the
Side value is 8 bits, and can range from 0 to 255 (256 numbers); the
Cylinder is 10 bits, and can range from 0 to 1023 (1024 numbers); the
Sector is 6 bits, and can range from 1 to 63 (63 numbers). (Note that zero
is not a valid sector number.) This means the maximum address on the disk
is Side 255, Cylinder 1023, Sector 63. The number of sectors is 256 X 1023
X 63, or almost 16.5 million sectors. Standard sectors are 512 bytes, so
we have a size of 7.87GB.
That's the point: The BIOS cannot access anything beyond the first 7.87GB
of the hard disk. If any critical boot data, such as the files NTLDR,
NTDETECT or BOOT.INI, get moved to a point more than 7.87GB from the start
of the hard disk, your computer will not boot. Anything that moves one of
the critical files may cause the problem; you may copy the file from
another partition, or you may edit the file. But you will not be aware of
any problem till the next time you boot.
You are vulnerable to this if the partition on which Windows NT is
installed is larger than 7.87GB, or if this partition is not the first
partition on the disk and the total of this partition and all of the
partitions before it exceeds 7.87GB.
Fixing the Problem
First thing is to boot up the computer using a boot floppy. This is simply
a floppy formatted on a Windows NT machine (that is vital), and containing
copies of NTLDR, NTDETECT.COM and BOOT.INI. The BIOS accesses the floppy
and finds the data it needs, then the floppy starts Windows NT, and
everything runs fine. Of course, the next time you boot, the problem is
back, but this gets the machine up and running so you can get your regular
work done. Now you can schedule a time to fix it when you won't disrupt
production.
Now, to fix it. The problem is simply that some critical file lies beyond
the part of the disk which the BIOS can access. The simplest handling is
to use the BIOS to rewrite the file. Start with your Windows NT Setup
Floppies and CD, and proceed as if you were installing a second Windows NT
installation. When asked which folder to use, specify a new folder, not
the one that the existing Windows NT is in. When asked if you want to
check the hard disks for errors, select "yes". Once this check is done,
you can abort the new installation and Windows NT will boot up
successfully.
Another handling is to move the critical files back closer to the beginning
of the disk. This can be difficult because you really don't know where the
files will be placed when you copy or move them. However, the odds are on
your side if the partition lies mostly within the 7.87GB limit. Trial and
error will do it.
Preventing the Problem
The simplest prevention is to always have the boot partition as the first
partition on the hard disk, and ensure that it is less than 7.87GB. If
this is not feasible, take steps to ensure the critical files will not be
moved. If the partition is in NTFS format, set the access on those files
so that only an administrator can access them, and if you are using a
defragmenter such as Diskeeper, add the critical files to the
defragmenter's exclusion list.
Lance Jensen
Technical Support Manager
Executive Software International, Inc.
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