Date: Tue, 01 Jun 2004 13:37:49 +0200 From: roman <rcher@inter.net.il> To: freebsd-questions@freebsd.org Subject: Disk geometry salad... Message-ID: <40BC6A8D.10403@inter.net.il>
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Hi, I would like to try FreeBSD but recently I've encountered several problems with the detection of my hard drives' geometry, so I have a few questions. I hope this is the right place to ask... First I would like to say that my understanding of this issue is minor, so if my questions seem stupid, I apologize in advance. I have two Western Digital hard drives, (1) WD400BB (40GB) and (2) WD300BB (30GB) and an Asus CUS-L2C motherboard (Intel 815EP chipset). The manufacturer website doesn't provide the CHS geometry for the drives, but lists the number of LBA sectors for each drive. For (1) it's 78,165,360 sectors * 512 bytes resulting in about 40.02 GB. For (2) it's 58,633,344 sectors * 512 bytes resulting in about 30.02 GB. On the first drive I currently have Windows XP, the second drive is empty. Western Digital's diagnostic utility for Windows detects the CHS geometry of the drives as (1) 4865/255/63 and (2) 3649/255/63 and confirms that the number of LBA sectors is identical to the manufacturer specification. FreeBSD 5.2.1 detects the CHS geometry (When it boots, there's a listing of the hard drives and the CHS geometry, but no LBA sectors) as (1) 77545/16/63 and (2) 58168/16/63. I have several questions regarding this. 1) What is the difference between a geometry of 58168/16/63 and 3649/255/63, why did the diagnostic utility detect the latter form, while FreeBSD detected the former (Also, Linux 2.4 detects the geometry as 3649/255/63)? 2) When installing FreeBSD, sysinstall warns that a geometry of the first drive (1) as it detects it (77545/16/63) is incorrect and can't be used. It automatically replaces the values with 4865/255/63. The problem is that after replacing the geometry with 4865/255/63 the number of LBA sectors (as listed in the Disk Slice editor) becomes lower than the manufacturer spec (78,156,225 instead of 78,165,360). What does this mean? 3) I tried installing FreeBSD on the second drive. Sysinstall didn't complain about the geometry of 58168/16/63 and I was able to install. The interesting thing is that when I started the installation program of Fedora Core Linux (Had to check something, and it was FC1 which means 2.4 kernel) it complained about an incorrect partition table that was generated by a tool that didn't have the right BIOS geometry. When I reinstalled FreeBSD on the same drive, but changed the geometry from 58168/16/63 to 3649/255/63, and launched the Fedora Core setup again - it didn't complain! Why is that?
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