Date: Thu, 26 Aug 2010 18:33:04 -0700 From: Doug Barton <dougb@FreeBSD.org> To: freebsd-fs@freebsd.org Subject: Difference of opinion about my disk geometry Message-ID: <4C7715D0.10604@FreeBSD.org>
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Howdy,
What I've done for years in order to create a dual-boot between windows
and FreeBSD, with one shared fat32 data partition; is to boot the
FreeBSD install CD, create the 3 primary partitions, install FreeBSD,
install Windows into the 1st primary partition, then boot the FreeBSD CD
again and install the boot mgr. My rationale for this is that we
(FreeBSD) know more about modern disk geometry than Windows XP does, and
this method has always served me well.
What I've done now is purchase a new HD for my laptop because the old
one was starting to act dodgy. It's a 250 GB Hitachi Travelstar, SATA
300 in case anyone cares (which is the same as what was installed by
Dell, except the old one was 100 GB). Since I have more space I'm
attempting to experiment with more stuff as you may have seen from my
other posts. However, FreeBSD disagrees with Windows and Linux about
what the right geometry should look like. Depending on which OS I use to
create partitions I get various errors about whether or not things end
on cylinder and/or track boundaries. This does not seem like a good thing.
Below are what the various OS' think about the disk. (Ignore the fact
that the 3rd partition has an unknown type, that used to be a FreeBSD
partition that seems to have been mangled by grub2, which I'm going to
fix later.) When I run FreeBSD fdisk from sysinstall I get the following
message:
It is safe to use 484521/16/63 as the disk geometry blah blah blah, Do
you want to change this?
I've been saying no, but now I think what I want to do is say yes, and
change it to 30401/255/63 which is what Windows and Linux think it is,
and repartition the whole drive. Does that sound reasonable?
Of course this prompts me to ask the questions of why are we looking at
this differently than Windows and Linux, and what are the
advantages/disadvantages to the 2 methods?
Thanks again,
Doug
Windows:
Sectors/Track 63
Size 232.88 GB (250,056,737,280 bytes)
Total Cylinders 30,401
Total Sectors 488,392,065
Tracks/Cylinder 255
Linux:
fdisk -l
Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Device Boot Start End Blocks Id System
/dev/sda1 1 3264 26214016+ 7 HPFS/NTFS
Partition 1 does not end on cylinder boundary.
/dev/sda2 3264 18276 120587585+ f W95 Ext'd (LBA)
/dev/sda3 * 18277 27414 73400166 b5 Unknown
Partition 3 does not end on cylinder boundary.
/dev/sda4 27414 30402 23996448 a5 FreeBSD
Partition 4 does not end on cylinder boundary.
/dev/sda5 3264 16318 104860255+ 6 FAT16
/dev/sda6 16319 16971 5242880 83 Linux
/dev/sda7 16971 17232 2096128 82 Linux swap / Solaris
/dev/sda8 17233 17493 2096128 83 Linux
/dev/sda9 17494 18276 6288384 83 Linux
fdisk -c -l
Device Boot Start End Blocks Id System
/dev/sda1 1 3264 26214016+ 7 HPFS/NTFS
/dev/sda2 3264 18276 120587585+ f W95 Ext'd (LBA)
/dev/sda3 * 18277 27414 73400166 b5 Unknown
/dev/sda4 27414 30402 23996448 a5 FreeBSD
/dev/sda5 3264 16318 104860255+ 6 FAT16
/dev/sda6 16319 16971 5242880 83 Linux
/dev/sda7 16971 17232 2096128 82 Linux swap / Solaris
/dev/sda8 17233 17493 2096128 83 Linux
/dev/sda9 17494 18276 6288384 83 Linux
FreeBSD:
******* Working on device /dev/ad0 *******
parameters extracted from in-core disklabel are:
cylinders=484521 heads=16 sectors/track=63 (1008 blks/cyl)
Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=484521 heads=16 sectors/track=63 (1008 blks/cyl)
Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 7 (0x07),(OS/2 HPFS, NTFS, QNX-2 (16 bit) or Advanced UNIX)
start 63, size 52428033 (25599 Meg), flag 0
beg: cyl 0/ head 1/ sector 1;
end: cyl 1023/ head 15/ sector 63
The data for partition 2 is:
sysid 15 (0x0f),(Extended DOS (LBA))
start 52428157, size 241175171 (117761 Meg), flag 0
beg: cyl 1023/ head 254/ sector 63;
end: cyl 1023/ head 254/ sector 63
The data for partition 3 is:
sysid 181 (0xb5),(unknown)
start 293603940, size 146800332 (71679 Meg), flag 80 (active)
beg: cyl 1023/ head 255/ sector 63;
end: cyl 1023/ head 15/ sector 63
The data for partition 4 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
start 440404272, size 47992896 (23434 Meg), flag 0
beg: cyl 1023/ head 255/ sector 63;
end: cyl 1023/ head 15/ sector 63
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