Recovering lost disk geometry

Hello!

I'm having problems trying to get an old hard disk configured so that BIOS
can boot the OS as it was before removing the CMOS battery. I know I
should have put down the correct setting before pulling the battery, but I
had forgotten what the PCs of the mid 90's were like... Too bad the BIOS
doesn't have auto mode for disk geometry (old Siemens-Nixdorf PCD-4H
486DX) and the CHS parameters reported by the drive manufacturer don't
seem to work. Booting up always end with "NO OS" message...

The drive is Western Digital WDAC1210-00F, with the following info on
the cover: C/H/S: 989/12/35. I verified this from the web. The disk should
thus be about 202 MB (or 212*10^6 B) and have max 415380 sectors. From
what I recall from the running system, it couldn't have been configured
much smaller, since there was about 100-150 MB of free space beside an
ancient SCO Xenix and Informix database installations.

The reason I even bother with this is the system should run still for one
year as a information db for telephone operators, and I just succeeded in
reviving a messed up database on the same system. I would like to either
somehow dump the partition on another disk or to figure out the correct CHS
geometry for the disk. The disk can be attached either to Linux or Windows
workstation, if that helps.

I searched the Net for quite a while and among others, found a utility
called TestDisk (v.5.0), which (at least I understood so) should be able
to locate lost partitions. It did, in fact, find one on the disk. It said
after selecting Analyze from the main menu:

----(manual screencopy ----

disk 80: CHS 989 12 35 - 202 MB

4 * XENIX root 0 1 4 987 3 11 414618
Bad ending sector

-----

I presume this means the partition starts at 0/1/4 and ends at 987/3/11,
and probably the last would be the sector count for it.
While searching for info I found that the 1st primary partition should
start at 0/1/1, but I don't know if the disk was actually partitioned
bearing that in mind. I'm also aware that partitions should (in many
cases) end on cylinder boundary, which is still quite abstract idea for
me. However, I don't know whether Xenix used that rule.

If someone could help me with this - either by checking the geometry and
other BIOS settings from a similar factory installed system with the same
drive (if there is one anywhere anymore), or by directing me to a good
explanative resource on the subject, or by giving a method of figuring out
the correct geometry based on what can be found from the disk - I would
be very happy
Also, if someone has a working crystall ball, I'd appreciate a quick peek


Best regards,
Esa


--
Esa Tikka --- esa dot tikka at lut dot fi ---
Vote against spam in EU @ http://www.politik-digital.de/spam

Hello Esa,

On Wed, 25 Feb 2004 18:46:09 UTC, Esa
wrote:

I'm having problems trying to get an old hard disk configured so that BIOS
can boot the OS as it was before removing the CMOS battery. I know I
should have put down the correct setting before pulling the battery, but I
had forgotten what the PCs of the mid 90's were like... Too bad the BIOS
doesn't have auto mode for disk geometry (old Siemens-Nixdorf PCD-4H
486DX) and the CHS parameters reported by the drive manufacturer don't
seem to work. Booting up always end with "NO OS" message...

The drive is Western Digital WDAC1210-00F, with the following info on
the cover: C/H/S: 989/12/35. I verified this from the web. The disk should
thus be about 202 MB (or 212*10^6 B) and have max 415380 sectors. From
what I recall from the running system, it couldn't have been configured
much smaller, since there was about 100-150 MB of free space beside an
ancient SCO Xenix and Informix database installations.

OK, what I would do if I where you, is setting the disk to the
WD-supplied geometry
in the BIOS to start with. (that will make sure you see the whole
disk).

Then, with a program that can find partition-records, bottsectors and
so on,
scan the whole disk and analyse the results.

Most likely you will be able to determine the correct geometry as used
before from that. Changing to this geometry might solve your error
message on booting. The most likely cause for the error message
is the fact that translating from the entries in the partition tables
results
in the wrong sector being accessed to read the XENIX bootsector.

The reason I even bother with this is the system should run still for one
year as a information db for telephone operators, and I just succeeded in
reviving a messed up database on the same system. I would like to either
somehow dump the partition on another disk or to figure out the correct CHS
geometry for the disk. The disk can be attached either to Linux or Windows
workstation, if that helps.

You can use my DFSee program for this analysis (and recovery if
needed).
It is a single distribution that contains a DOS, Windows and OS2
version.

You can either leave the disk in the current system and use a bootable
DOS
diskette, or mount the disk in a Windows (NT,W2K or XP) workstation.

For the DOS solution, you can download a self-extracting
diskette-image
that contains FreeDOS and the DFSDOS executable from:

http://www.dfsee.com/dfsee/dfsee6xx_dsk.zip

You can run the executable enclosed in the ZIP file on any DOS or
Windows
commandline, and it will create the bootable disk on a (formatted)
diskette in the A: drive.

If you mount the disk in a Windows system, you need the DFSWIN.EXE
executable
and DFSUNFD.DFS script from the standard disrubution:

http://www.dfsee.com/dfsee/dfsee6xx.zip

In both cases, you can search for partitioning info using the menu:

Actions - Find partitions, All sectors - 1 ... (select the disk)

As an alternative you can ru the DFSUNFD script (BAT file) as shown
below:

++++++++++ Runing the DFSUNFD procedure

You would need the DFSUNFD.DFS script that comes with DFSee, plus:
- For DOS or Win9x bootdiskettes DFSUNFD.BAT and DFSDOS.EXE.
- For Win-NT/2000/XP DFSUNFD.BAT and DFSWIN.EXE
- For OS/2 DFSUNFD.CMD and DFSOS2.EXE

You simply run the batch-file (.BAT or .CMD) without any parameters
and it will
collect FOUR files for every physical disk you have. (DFSUNFDI.*)

Based on the DFSUNFDI.* information a recovery script can be created.

You will most likely need assistance to do that, and that DOES require
you to have (or buy) a registration, see:

http://www.dfsee.com/dfsee.htm#register

Send all DFSUNFDI.* files (zipped to one file) to DFSee support at:



++++++++++


I searched the Net for quite a while and among others, found a utility
called TestDisk (v.5.0), which (at least I understood so) should be able
to locate lost partitions. It did, in fact, find one on the disk. It said
after selecting Analyze from the main menu:

----(manual screencopy ----

disk 80: CHS 989 12 35 - 202 MB

4 * XENIX root 0 1 4 987 3 11 414618
Bad ending sector

TestDisk might be comparable to DFSee (in finding partitions :-)
but I am not familiar with it. From the result, it seems that
partition
was not aligned to cylinder boundaries.


-----

I presume this means the partition starts at 0/1/4 and ends at 987/3/11,
and probably the last would be the sector count for it.
While searching for info I found that the 1st primary partition should
start at 0/1/1, but I don't know if the disk was actually partitioned
bearing that in mind. I'm also aware that partitions should (in many
cases) end on cylinder boundary, which is still quite abstract idea for
me. However, I don't know whether Xenix used that rule.

I think XENIX did NOT obey those rules, which will make determining
the correct geometry a bit harder. However, I do think they did use
a regular bootsector, so finding that, and comparing its position to
the entry in the partition table (MBR sector) should be enough ...



If someone could help me with this - either by checking the geometry and
other BIOS settings from a similar factory installed system with the same
drive (if there is one anywhere anymore), or by directing me to a good
explanative resource on the subject, or by giving a method of figuring out
the correct geometry based on what can be found from the disk - I would
be very happy

There is some info (and links) about partitioning on my web-site, and
some more explanations about geometry in the DFSee documentation.

There is lots of info on the WEB too, but it is hard to find, and
often hard to understand ...


But I'll be happy to assist you :-)


Also, if someone has a working crystall ball, I'd appreciate a quick peek


Sorry, no crystal ball here :-)

Regards, JvW

--
Jan van Wijk; Author of DFSee: http://www.dfsee.com