On Fri, 31 Mar 2000, Mike Carbonel wrote:
..
> hi,
> need some help... i'm installing redhat 6.0 on my
> 12Gb seagate harddisk. but redhat only detects 8Gb
> size. is redhat not capable of handling above 8Gb of
> harddisk size??? thank you in advance and good day to everyone.....
The following should fix it:
(in lilo.conf)
$ cat /etc/lilo.conf
boot=/dev/hde
append="hde=3467,255,63"
^^^^^^^^^^^^^^^^^^^^^^^
map=/boot/map
install=/boot/boot.b
linear
vga=773
prompt
timeout=50
image=/boot/vmlinuz-2.2.14
label=linux
root=/dev/hde1
read-only
Note that the magic line is the one with "append" in it. The problem is
not that redhat is incapable of using >8Gb of disk, it is that the BIOS
cannot report >8Gb of disk. For example (on my machine):
# /sbin/hdparm -i /dev/hde
/dev/hde:
Model=ST328040A, FwRev=3.07, SerialNo=7BY01XJ6
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=0
BuffType=0(?), BuffSize=512kB, MaxMultSect=16, MultSect=16
DblWordIO=no, maxPIO=2(fast), DMA=yes, maxDMA=2(fast)
CurCHS=16383/16/63, CurSects=-66060037, LBA=yes, LBAsects=55704096
tDMA={min:120,rec:120}, DMA modes: mword0 mword1 mword2
IORDY=on/off, tPIO={min:240,w/IORDY:120}, PIO modes: mode3 mode4
Timing buffer-cache reads: 64 MB in 0.57 seconds =112.28 MB/sec
Notice the RawCHS: its 16383 cylinders, 16 heads, 63 sectors. At 512 bytes
per sector, (16383 x 16 x 63 x 512) = 8455200768 bytes or roughly 8.4Gb.
Thats a BIOS limitation.
However, what is REALLY important is the total number of LBA sectors (in
the above case, LBAsects=55704096 or 28520497152 bytes [28Gb]). What you
need is to pick the correct CHS values so that the total number of sectors
equals the reported number of LBAsects.
For my case, I chose (actually, I didnt choose.. Windoze chose for me and
I followed), append="hde=3467,255,63" which means..
Cylinders = 3467
Heads = 255
Sectors = 63
which totals (3467 x 255 x 63) = 55697355 sectors which is a bit less than
the reported LBAsects but it's the closest I could get. Why is this
allowed? because ALL current drives report "fake" CHS values just to
satisfy the BIOS and the partitioning software.
For example, my Seagate Barracuda has only 4 platters = 8 heads, but you
can use any number of heads you want as long as the total number of
sectors <= the LBAsects of the drive. However I believe heads cannot
exceed 255 and sectors cannot exceed 63.
For installing on your hard disk, add
hde=CYL,HEAD,SECTS
to the LILO prompt when initially booting from the install CD. This will
allow your entire drive space to be used.
Important note: windoze 98 has its own idea of what CHS to apply to a
large hard drive, because, as I've pointed out above, the CHS values are
more-or-less arbitrary. So if you are doing a dualboot install, make SURE
to install Windoze FIRST.
You can force Linux to accept any arbitrary drive geometry via LILO
command line or lilo.conf, whereas Windoze will use its own rules for
setting up CHS and wont pay any attention to you. All the OS's on your
hard drive must agree on what CHS assignment to use, otherwise you've got
corrupted partition table and corrupted data.
sidenote: LBA = linear block address, you can consider the entire hard
drive to be a linear series of blocks, addressable via block number (the
LBA sector number). However, traditionally the drive is accessed via
cylinders, heads, and sectors. The CHS represents a coordinate in 3-space,
which can be mapped into the one-dimensional LBA coordinate system as
LBA sector = f(C,H,S)
You have a mapping f() between a given coordinate (C,H,S) to the linear
mapping. Think of it as a Laplace transform for hard drives! this f()
mapping has the drive's current CHS as constant factors. So by changing
the CHS, the linear block pointed to by the same (C,H,S) coordinates
changes. That's why all your OS's have to agree on what CHS assignment to
use.
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