SR News: Win95/FDISK/Extended Partitions and Possible Data Corruption


BEWARE OF WINDOWS 95 (DOS 7) FDISK

(updated June 3, 1997)

We've had reports from Integrity Master customers that their newly purchased
(and partitioned with Windows 95 FDISK) disks are unreliable.  (Note,  these
problems are not related to Win95 OSR2 (service  release  2  which  supports
FAT32.) This was particularly troubling because these disks were  brand  new
and shouldn't be having problems--yet Integrity Master  was  detecting  file
corruption on these disk.

Initially these problems looked exactly like hard disk failure  or  in  some
cases like memory or motherboard  problems.  The  symptoms  included  system
hangs and occasional inability to boot.

Some users found cross-linked clusters and used Scandisk, Norton Disk Doctor
or other utilities to "fix" there disks. After doing this, the users were in
a "fix"--there was now massive damage to the files on their disks.

The problem stems from a bug in the way the Windows 95 (actually  MS-DOS  7)
handles extended partitions created by the  Windows  95  FDISK  program  for
large disks (with more than 504 megabytes). Bugs in the Windows  95  (MS-DOS
7) hard disk drivers can cause data corruption in this situation. If you are
running an integrity checker it will report  corrupted  files  and  possibly
directories.

If you suspect this problem, please do NOT run Scandisk or one of  the  disk
fixup utilities since this can make the situation much worse.

ARE YOU AT RISK?

You are vulnerable to this problem if you meet all the following criteria:

     You are running Windows 95 and You have an IDE hard disk with more  504
     million bytes using LBA. (LBA is the address translation  support  that
     allows the BIOS on these PCs to support more than 504mb.) The hard disk
     has more than one logical partition created by  the  Windows  95  FDISK
     program.

Microsoft reports that data damage may result when you exit the  Windows  95
graphic user interface to the MS-DOS command line without rebooting the PC.

If you suspect you have this problem be very careful since it can result  in
loss of all data in your extended partitions. An integrity checker  such  as
Integrity Master should be able to spot any data corruption before  it  gets
serious. (Microsoft documents this problem in their PSS ID Number: Q148821).

SOLUTIONS TO THE PROBLEM

If you use the /X parameter on FDISK (i.e., "FDISK /X" )when  you  partition
your hard disk under Windows 95 (or DOS 7), FDISK will user the older  style
extended partitions and you (according to Microsoft) will not be exposed  to
this problem. Reports from our customers seem to support the contention that
this gets around the problem. Note, that  if  you  already  have  partitions
created with Windows 95's FDISK, you can recreate them with "FDISK  /X"  but
you will need to reload all data into these partitions from a  backup.  Make
absolutely  sure  you  have  a  good  backup  (or  preferably  two!)  before
attempting this.

Microsoft is working on the problem and has  posted  "fixes"  on  their  web
site. (See technet document Q148821 and file DSKSUPD.EXE).

                                    Copyright c 1997 Stiller Research.
                                    Document Last Modified June 3, 1997.

[=- 㡫  ୠ ᪨ 蠫 //  #2 //  1998  -=]
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