To: opendos AT delorie DOT com X-Comment-To: Rob McGee Cc: i812 AT iname DOT com References: <20010314002926 DOT B3024 AT sl7> Message-Id: <2.07b7.14Z6R.GA6TFH@belous.munic.msk.su> From: "Arkady V.Belousov" Date: Wed, 14 Mar 2001 15:30:53 +0300 (MSK) Organization: Locus X-Mailer: dMail [Demos Mail for DOS v2.07b7] Subject: Re: [ot] disk geometry mismatch? Lines: 69 MIME-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Transfer-Encoding: 8bit Reply-To: opendos AT delorie DOT com X-Comment-To: Rob McGee Hi! 14-ํมา-2001 00:29 i812 AT iname DOT com (Rob McGee) wrote to opendos AT delorie DOT com: RM> could no longer access the hard drive. It's a WDC AC35100L which is RM> C/H/S 10672/15/63, LBA'ed to 627/255/63. Identify drive from a Linux ___________________^^____________________^^ RM> I had a CD of Norton Util. 95 v. 2 (FAT32-aware) and tried ndd.exe. It RM> offered to try to recover a partition of 812MB. I declined the offer and RM> tried diskedit.exe instead. The first 63 sectors were all 0's. (63 spt, RM> of course. Is that normal?) Yes. FDISKs usually start first partition from next free head, not right after MBR (from the next sector): ______________O\_/_________________________________\_/O______________ No Drive Start End MB Status Type 1 C: 0 203 100,3 A PRI DOS 2 -- 204 1022 403,1 N EXT DOS _____________________________________________________________________ O/~\ /~\O ______________O\_/_________________________________\_/O______________ BIGDOS ไม  1 0 1  15 203 63  63 205569 _______________^_______________________________________________^^ EXTEND ๎ลิ 0 204 1  15 1022 63  205632 825552 _____________________________________________________________________ O/~\ /~\O This picture from diskedit better to slightly modify by swapping heads and tracks: 0 1 1  203 15 63  63 205569 ____^ 204 0 1  1022 15 63  205632 825552 This disk pointed in BIOS setup as 1023/16/63. RM> The 64th sector showed what looked to my untrained eye like some RM> filesystem information. There was a string "FAT32" and the volume label RM> as it was before the crash. There most probaly boot sector of first partition. RM> Finally this afternoon I came up with the hypothesis of a disk geometry RM> mismatch. That some parameters had been manually entered in the dead RM> motherboard's CMOS settings, and they weren't quite correct, but close RM> enough that the drive went along with it. RM> Does this hypothesis sound right? Most probably. I already meet such case - if point disk, partitioned in CHS mode, as LBA disk in BIOS setup, then it look worngly. RM> If so is there anywhere I might be RM> able to find a clue about the disk geometry parameters used? I'm affraid this may be done only manually. But you may try to decide disk geometry from partitions parameters (look above) or try special disk recovery utility like Tiramisu. You may also try to talk with Brian Refsnyder - author of FreeFDISK. RM> I'm afraid RM> that my "fdisk /mbr" might have rendered the thing unbootable though. Most probably no. /MBR option brings FDISK to refresh MBR _code_ and should remain partition table itself untouched.