When units are set to chs, parted accepts and prints sector numbers on the assumption that they index from 0. In fact, sector numbers in CHS values should index from 1 (unlike cylinder and head numbers, which do index from 0). Of course, in the context of LBA, indexing sectors from 0 is correct.
I found this message in the bug-parted list from September 2004: http://lists.gnu.org/archive/html/bug-parted/2004-09/msg00028.html Here the author, a parted developer, wrote: > I think it is stupid to count [sectors] from 1. I unilaterally > decided to count from 0 (just like cylinders and heads are). Well, I (and I suspect many other people) "just know" what I asserted above. In the interests of getting parted changed, I've made an attempt to find the source documentation. The original writer to the above thread (who submitted a patch) referred to http://www.win.tue.nl/~aeb/linux/Large-Disk-3.html as providing an instance of the normal formula for translating CHS to LBA, "c*H*S + h*S + (s-1)". That's an impressive document, but not authoritative. Even more impressive, but again, not ultimately authoritative, is this: http://www.freeopenbook.com/upgrading-repairing-pc/ch07lev1sec4.html#ch07lev3sec3 This thorough examination of the Windows 7 MBR provides a typical example, showing the first partition starting at (LBA/relative) sector 2048 or CHS 0,32,33, implying that CHS sectors start at 1: http://mirror.href.com/thestarman/asm/mbr/W7MBR.htm#INTRO. I tested parted on a Windows 7 MBR, and parted printed 0,32,32. This: http://www.viralpatel.net/taj/tutorial/chs_translation.php#chs_translation_algo quotes from the ATA-2 document: > LBA = ( (cylinder * heads_per_cylinder + heads ) * sectors_per_track ) + sector - 1 The ATA-2 document is a publication of the INCITS T13 Technical Committee: http://www.t13.org which "is responsible for all interface standards relating to the popular AT Attachment (ATA) storage interface utilized as the disk drive interface on most personal and mobile computers today." Unfortunately, the standards are not free, even if the relevant standard is still available for purchase. However, some draft documents remain on the public Internet. A proposed draft of ATA/ATAPI-5, dated 25 September 1998, is at http://t13.org/Documents/UploadedDocuments/project/d1321r0a-ATA-ATAPI-5.pdf. A later working draft, dated 11 May 1999, is on the related T10 (SCSI) Technical Committee's Web site: http://www.t10.org/t13/project/d1321r1-ATA-ATAPI-5.pdf. These documents state, in section 6.2 (Page 19): "A CHS address is made up of three fields: the sector number, the head number, and the cylinder number. Sectors are numbered from 1 to the maximum value allowed by the current CHS translation but shall not exceed 255. Heads are numbered from 0 to the maximum value allowed by the current CHS translation but shall not exceed 15. Cylinders are numbered from 0 to the maximum value allowed by the current CHS translation but cannot exceed 65,535." Note that this is talking about the drive doing the translation, for compatibility purposes, between its native LBA addressing and the host's CHS addressing. ATA/ATAPI-6 obsoleted CHS translation, as the draft at http://www.t13.org/documents/UploadedDocuments/project/d1410r3b-ATA-ATAPI-6.pdf (dated 26 February 2002) says in section 6.2 (Page 22): "In standards ATA/ATAPI-5 and earlier, a CHS translation was defined. This translation is obsolete but may be implemented as defined in ATA/ATAPI-5." ............ So I hope I've demonstrated that CHS sectors indeed index from 1. It's not tidy, it's not elegant, but it's a published, albeit obsolete, standard, and not a matter of opinion. Please could the patch referred to above be considered? Maybe http://parted.alioth.debian.org/cgi-bin/trac.cgi/ticket/218 is also relevant. It's a small point, and becoming less and less relevant, of course, but there are enough quirks and pitfalls in the area that we don't need an avoidable one. Whether or not the code is changed, I suggest the manual should be updated to make clear the distinction between CHS and LBA sector numbering. _______________________________________________ bug-parted mailing list bug-parted@gnu.org http://lists.gnu.org/mailman/listinfo/bug-parted
