Contents of the DOS6PREP.TXT file
CheckIt PRO: CKMEDIA Applet
Copyright (c) 1993 TouchStone Software Corporation. ALL RIGHTS RESERVED.
FREE License to Use the CheckIt PRO: CKMEDIA Applet
TouchStone Software Corporation (developer of CheckIt) is pleased to
provide you a FREE license to use the CheckIt PRO: CKMEDIA.EXE applet
(mini-application program), provided that you do not modify the program in
any way. You may make as many copies of the program as you need for your
own use or to pass along to others as long as you also include this text
file in its original form. Neither the program or this file may be
(resold) distributed as part of any commercial venture.
DOS 6.0 and Data Corruption Problems
There has been a lot of discussion in the press lately regarding DOS 6.0
and possible problems with DoubleSpace compression. In the process of doing
our own research for CheckIt PRO, we did indeed encounter some problems
with data loss, but not as a direct result of DoubleSpace compression. The
specific problems that we identified were actually due to installing
DoubleSpace on a drive with latent errors, or physical media defects which
caused some data areas on the drives to be marginal for storing data
safely. The problems that occurred on our DoubleSpace volumes could have
been prevented by testing the drive to detect unsafe data areas (clusters),
then re-formatting or re-marking the clusters as bad to prevent any file,
especially a DoubleSpace volume, from using them.
The CKMEDIA.EXE applet finds disk surface and file structure problems with
your HD, FD, or SyQuest/Bernoulli drives. These latent errors may cause
data corruption once you format them with DOS, or begin using DoubleSpace
or SmartDrive. The CKMEDIA applet is completely harmless; it creates a
report but doesn't alter the disk. We recommend you use it in conjunction
with CHKDSK, which finds corrupted cluster links. To get started, type:
C:>DOS6PREP To Run CKMEDIA & CHKDSK from a BAT file
C:>CKMEDIA C: To Test Drive C
C:>CKMEDIA /? To See program Help
C:>TYPE CKPRO.RPT | MORE To View default program output
C:>CHKDSK > CHKDSK.RPT To Run CHKDSK & create file
If you want to learn a little more about the DOS data corruption problems
we've found, or how this procedure can help you avoid them, read on...
Problems Created by the DOS FORMAT Command
Older MFM and RLL-encoded drives are more likely to experience data-loss
because of the lack of error detection built into the drive. Newer
technologies such as IDE has intelligence for managing bad tracks and
therefore become less susceptible, although not impervious. Before you
begin using a drive for data you should always first test it rigorously to
eliminate any chance of potentially bad clusters being assigned for use by
DOS. This preparation step is particularly crucial for compressed drives.
In our testing, we backed up an existing MFM drive which had been in use
for a while. Several marginal clusters were detected over time by our
CheckIt hard drive test and therefore marked as bad in the FAT. Then we
performed a DOS FORMAT before installing DoubleSpace. This created a
special circumstance which not all users may be aware of. Incredible as it
may seem, the DOS FORMAT process does NOT preserve any entries marked as
"BAD" (FF7h for 12-bit FATs, FFF7h for 16-bit FATs) in the File Allocation
Table (FAT). All of the bad sector marks we had painstakingly applied with
Disk Doctor and DiskFix were gone. Instead of carrying forward this vital
information, the DOS FORMAT re-marked all of these bad clusters "Available
for Use". Subsequently, when we restored the data some of the bad sectors
were assigned to data files -- and others ended up being assigned to
critical areas like our DoubleSpace compressed drive. As we began to use
the drive again, errors occurred and the data files became irrecoverably
Another problem with the DOS 6.0 FORMAT is that it may even return to use
some of the sectors that have been marked as part of a Bad Track at the
low-level! During the format, it will re-read individual sectors that are
part of a marked track, and make the determination that some of them may be
useable (this is what's happening when you see the message "Trying to
recover allocation unit #"). However, the test performed by the DOS Format
is inadequate, and sectors may be returned to use that would fail more
rigorous tests, and will subsequently cause errors and data loss.
The lesson here is, try to avoid using FORMAT.COM, and make an effort to
mark bad sectors at the low-level. Even though no method seems completely
impervious to the DOS FORMAT process, at least with the low-level format
you have a much better chance of avoiding re-use of the bad sectors. We
recommend that the entire track which the bad cluster occupies be marked
out at low-level -- you can do this with the formatter supplied with your
drive, or with the Checkit PRO Universal Low-Level Formatter. If you
aren't willing to backup your drive do another low-level format, then
retest your drive using our free CKMEDIA utility to create a list of the
bad clusters, and purchase a utility to re-mark them each time you use the
DOS FORMAT. We plan to include a replacement for the DOS format command in
a future release of CheckIt PRO.
Media Problems and DoubleSpace: The use of disk compression magnifies the
potential for problems if a drive is less than perfect. Once installed,
DoubleSpace creates a single large file (the size depends on how much of
your drive you want to compress) which becomes the new DoubleSpace volume.
This volume contains its own file structure for managing files that have
been compressed as well as the compressed files themselves. Since the
DoubleSpace volume occupies a significant portion of your drive, the
chances of a "marginal" data cluster being assigned to it for use are
somewhat substantial. More of disk space is now devoted to critical areas
such as the DoubleSpace's internal subset of the FAT and header data.
Furthermore, more data is packed onto each cluster, and it is more
difficult for data-recovery utilities to unscramble errors in these areas.
Cross-Linked Files: When data errors occur, they may be caused by -- or
they may result in, "cross-linked files". This term refers to a file which
references a cluster which is also referenced by another file (a cluster
should only ever be referenced by one file). Once a cluster has become
cross-linked, a future read/write operation may cause either or both of the
files to become unreadable and your utilities or applications may crash
when attempting to access the file. Since DoubleSpace creates an entire
disk drive within a single file, a cross-linked cluster within this special
file can create major problems, and even cause the loss of all the data in
the compressed drive, if the bad cluster is within one of its critical
areas (the headers, buffer area, or compression table). Cross-linked files
may be created as an indirect result of re-use of bad clusters caused by
the DOS FORMAT command, because a read error by an application may cause it
to crash and corrupt the FAT. They can also be caused by using the
SmartDrive caching utility in delayed-write mode, and then having your
system crash, rebooting, or turning it off before all the data is written
out and the file closed properly. A third method we have seen involves
running DOS programs under Windows and swapping between them during file
I/O. The cross-linked or corrupted-link clusters are a serious problem
likely to get worse; and we recommend that you run CHKDSK at least daily to
prevent this from happening, if you use your computer frequently with
DoubleSpace or SmartDrive.
File Names with Special Characters: We also found, in reviewing some of
these problems with other developers, that the DoubleSpace installation
program is especially sensitive to the use of illegal characters in DOS
filenames. If any filenames or directory names on the your disk contain an
illegal DOS filename character, corruption may likely result. We added the
capability of reporting these names to our CKMEDIA applet, to help with
Test your Disks with CKMEDIA: The CKMEDIA.EXE applet is a specialized
version of the CheckIt Hard Drive Test, which we have improved and extended
to cover the range of DOS 6.0 & DoubleSpace problems described above. In
this version, CKMEDIA.EXE not only checks the entire disk surface for
problems, but differentiates between clusters/sectors already marked bad at
the low-level format and those marked at the DOS level (as well as, of
course, bad clusters that are not marked at all). It also shows the type
of use for each bad cluster -- so you can see right away if any critical
areas are involved. Finally, we added a check on filenames, so CKMEDIA.EXE
will list the full pathname of all files with special characters in the
NOTE: CheckIt 3.0 and CheckIt PRO also include excellent programs to
use for finding surface errors -- the CKMEDIA.EXE applet simply adapts
that technology to this special situation. For best results, if you
have those programs you can run them too, as they include more specific
tests of the drive mechanics and may detect additional errors. And
while you may have other utilities for finding disk errors, we strongly
recommend that you use CheckIt or the CKMEDIA.EXE applet because the
tests they perform are rigorous and may discover errors missed by other
programs. In addition, the other utilities generally do not show all
the information you need to determine which sectors need to be re-
marked, the relationship between logical clusters and physical sectors,
or whether bad sectors are currently being used for any critical disk
areas. Also, be aware that the results of tests may vary slightly. We
recommend taking the pessimistic perspective on all errors and mark all
the sectors/clusters that fail any test.
How to Use CKMEDIA
The CKMEDIA.EXE applet can be used as a command at the DOS prompt, or from
a DOS batch file with a variety of output options. The interface options
also allow it to be called from another program. This syntax is typical of
the 20 or so applets that are included with CheckIt PRO. To view this
syntax when you're using the program, simply type CKMEDIA with no
parameters and a help screen will be displayed.
CKMEDIA - DOS Drive Structure/Media Test CheckIt PRO: v1.07
Copyright (c) 1989-1993 TouchStone Software Corp *ALL RIGHTS RESERVED*
Usage: CKMEDIA drivename [/T:#test] [R:start-end] [/F:filename,type]
[/I:interface] [/O:dest,format] [/N:"note"]
drivename Letter-name of drive(s) to test (A, C, etc., up to four).
/T:#[test] Run # iterations of the specified phases (default=1bfrdn).
test One or more of the following:
b = boot sector f = FAT sectors
r = root directory d = data clusters
n = naming check c = CHKDSK results
/R:start-end Test this range of clusters (ie /R:2-1000).
/F:filename,type Store bad entries to this file.
type b = bad tracks (BIOS geometry)
c = bad clusters for marking at DOS level
f = invalid file and directory names
/I:s[a] Silent. Run with no program interface.
/I:t[a] Terse. Simple display output (default).
/I:b[a] Boxed test dialog for batching.
(the optional [a] sounds a beep on failures/anomalies).
/O:[dest,format] Send output to destination in the specified format.
dest Any valid DOS file or device name.
DOS devices include CON, AUX, PRN ,LPTx, COMx, and NUL.
format Any of the following:
a = ASCII format (default setting is /O:CKPRO.RPT,A).
j = Journal format. Used for debugging.
/N:"note" Add a note to the output. (i.e. /N:"This is a note")
Example: CKMEDIA C E /T:3bd /O:prn,a /O:ckpro.rpt,a /N:"Test Drives C & E"
To make the applet easier to use for those who are not familiar with our
syntax style, we have included a BAT file which illustrates how to use the
applet in combination with the CHKDSK utility (required to provide the
cross-link information). The BAT file to check drive C: is DOS6PREP.BAT:
CHKDSK C: > CHKDSKC.RPT
CKMEDIA C: /T:brnfdc /F:BADTRACK.RPT,B /F:BADCLUST.RPT,C
/F:BADFILES.RPT,F /O:CKMEDIAC.RPT,A /O:CKMEDIAC.JNL,J /N:"TEST HD C:"
If you use the BAT file, output from CKMEDIA will consist of up to 6 files:
CHKDSKC.RPT Report from CHKDSK on drive C:
CKMEDIAC.RPT Report of Test Results.
CKMEDIAC.JNL Journal (report) of step-by-step test progress.
BADTRACK.C Data file with the addresss of all bad sectors found.
BADCLUST.C Data file with the numbers of all bad clusters found.
BADFILES.C Data file with the pathnames of all bad filenames.
How to Use the CKMEDIA Report:
1. Boot Sector Test. If this test failed, you cannot boot from this
drive. You may use the disk to store programs and data files (only).
2. FAT Sector Test. If this test failed, you already have a very serious
problem which may not be able to be repaired. This test compares the
FAT and its backup copy, which should be identical.
3. Rootdir Test. If this test failed, you already have a very serious
problem which may result in the loss of at least some subdirectories.
4. Data Clusters Test. If this test failed (at least one unmarked bad
cluster), there will be a list of bad clusters in the output file. If
the bad cluster is in a critical area, it may already be too late --
but you can try to backup as much data as possible from the entire
disk, and then perform a low-level format before restoring the data.
When you perform the low-level format you will need to re-mark all the
bad tracks (if you use the CheckIt PRO universal low-level formatter,
it will use the data in the BADTRACK file and mark them
automatically). The low-level format markings will be safer in the
long run, if you continue to plan using DOS 6.0 because they are less
likely to be destroyed by the DOS FORMAT command. The CheckIt PRO
low-level formatter will format all types of drives, including ESDI,
SCSI, and IDE as well as MFM and RLL. On the other hand, you can also
use utilities like Disk Doctor to re-mark the Bad Clusters at the DOS-
level, but BEWARE: If you ever use the DOS FORMAT command again, all
your markings will be lost and you will be in danger again!
5. Filenames Check. If this test failed, there will be a list of
pathnames in the report file which contain illegal characters.
This problem is less serious. Simply change each filename to one
which has no illegal characters, unless your application must use the
name as it is currently specified. In that case, the file must be
moved off the drive to be compressed to another uncompressed drive.
6. CHKDSK Results. If this test failed, it means that your disk contains
cross-linked clusters. Examine the file named CHKDSK?.RPT to see the
cluster numbers which are currently cross-linked. You may be able to
recover, depending upon which files are affected. In general, you can
run the CHKDSK utility again, with the /F option to have that program
create a file with the data from the cross-linked cluster in it.
Examine this data and see if you can determine which file it belongs
to. This type of problem should be fixed IMMEDIATELY, before you use
your hard disk further.
7. CKMEDIA Data Files: The Bad Tracks, Bad Clusters, and Bad Filenames
data files are only created as needed. The Bad track file is
formatted for use directly by the CheckIt PRO Low-Level Formatter.
The Bad Cluster and Bad Filename file will be useful if you decide to
re-mark clusters at the DOS level, or change the filename using
You Really Ought to Get a Copy of CheckIt PRO!
CheckIT PRO is the diagnostic program of choice for most serious PC
technicians, and has recently been awarded PC Magazine's Editor's Choice
for System Reporting utilities. The retail CheckIt PRO product provides
not only many more diagnostic applets, but a pretty menu interface for
them, and customizable test scripts. Important features include:
CheckIt PRO: SysInfo
Over 50 charts, tables, and graphic displays that show:
* Detailed hardware component and software configuration data
* The most accurate IRQ Usage and I/O Address Map information
* CMOS Setup and DOS/Windows System File Editor
* Performance Benchmarks with User-Modifiable Comparison Library
* Built-In Technical Reference Library
CheckIt PRO: Tests & Tools
Hardware Diagnostics for:
* Comprehensive Testing of System Board, Memory, Hard Drives, Floppy
Drives, COM Ports, LPT Ports, Printer, Video, Joystick, Mouse, and
* Scripts for Quick Test, System Certification, and Burn-In
* Universal Low-Level Formatter for all types of hard drives
* Virus Scan that detects over 2,000 viruses including Polymorphic
* Create Rescue Disk function that creates a bootable floppy with copies
of your CMOS, System Files, Device Drivers, and Utility Programs
necessary to recover from a hard drive or system crash.
CheckIt PRO: Deluxe
This new package includes both volumes of CheckIt PRO described above, plus
a Tool Kit consisting of:
* 3.5" and 5.25" Mini-Spiral Floppy Drive Alignment Testing Disks
* Set of 3 Loopback Plugs for IRQ and external COM, LPT port tests
* Screwdriver, Cable Labels, etc.
Isn't it time for you to Get With the PROgram? CheckIt PRO is available at
most computer software resellers. To purchase a copy or find out the name
of the store nearest you, write or call:
TouchStone Software Corporation
2130 Main Street
Huntington Beach, CA 92648 USA
Phone: (714) 969-7746 or (800) 531-0450
And REMEMBER: When in Doubt, CheckIT OUT!