Help!!! I need to find the formula for calculating the amount of

cylinders on a hard disk. Could someone please e-mail me the formula?

Thanks in advance.

-Chris

Help!!! I need to find the formula for calculating the amount of

cylinders on a hard disk. Could someone please e-mail me the formula?

Thanks in advance.

-Chris

On 9 Apr 1996 23:31:25 GMT, Christopher B Jessen dumped the following to

comp.os.linux.setup:

Uhh.. this ain't any e-mail, but there ain't any formula for yourQuote:>Help!!! I need to find the formula for calculating the amount of

>cylinders on a hard disk. Could someone please e-mail me the formula?

>Thanks in advance.

cylinders :) ...except, of course, the fact that your hdd space in bytes

is C*H*S*512, where C,H and S are the number of cylinders, heads and

sectors respectively. so, we get number of heads by evaluating

Capasity/512*HS

;)

--

//Ed

%

But why did the chicken cross the road?

H.P. Lovecraft:

To futilely attempt escape from the dark powers which

even then pursued it, hungering after the stuff of its soul!

|> On 9 Apr 1996 23:31:25 GMT, Christopher B Jessen dumped the following to

|> comp.os.linux.setup:

|>

|> >Help!!! I need to find the formula for calculating the amount of

|> >cylinders on a hard disk. Could someone please e-mail me the formula?

|>

|> Uhh.. this ain't any e-mail, but there ain't any formula for your

|> cylinders :) ...except, of course, the fact that your hdd space in bytes

|> is C*H*S*512, where C,H and S are the number of cylinders, heads and

|> sectors respectively. so, we get number of heads by evaluating

|>

|> Capasity/512*HS

I've got a related question. I repartitioned a 1.7 GB micropolis drive

from a SUN to use under Linux, and fdisk reported a radically different

number of C,H, and S (842,128,32) from the numbers which were used on the

SUN (2394,15,96). Both sets of numbers give about the same capacity

and fdisk didn't complain about the need to set these by hand from the

extra functions menu, so I went ahead and used these apparently bogus

numbers. As far as I can tell, everything works OK, but I wonder ....

Why does this work? Am I in for trouble later on?

1. disk cylinders and alternate cylinders?

In Ultrix 4.3's /usr/include/sys/devio.h, I read:

: dev_size; /* number of blocks in the user area (#pc)*/

: ntracks; /* number of tracks per cylinder (#nt) */

: nsectors; /* number of sectors per track (#ns) */

: ncylinders; /* total number of cylinders (#nc) */

: attributes; /* Device attributes; see defs below */

However, on some other operating systems like DEC OSF/1 1.3 or SunOS 4.1.3,

I see a reference to "alternative cylinders" when getting the disk geomery

info via DEVGETGEOM ioctl(). What is an "alternate cylinder" and more

importantly for me, do you include the alternate cylinders in the total

number of cylinders or not?

To be even more pratical, what if I know the recommended number of cylinders

and alternate cylinders for, say, a "Quantum PD 1050" drive from a SunOS

/etc/format.dat file which includes cylinders and alternate cylinder

numbers. If I want to create an /etc/disktab entry for it under Ultrix, do I

use the number of cylinders or the cylinders+altcylinders number?

Thanks for any help. Beg, plead, whimper.

--

I don't speak for Swarthmore College | Computing Center, Swarthmore, PA, USA

"I post, therefore I am." -Rene Descartes on Usenet

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