Re: Ahah, 4096 blocksize disk is not recognised under Linux?

[Michel <mi...@da...>]

On Fre, 2003-01-10 at 01:04, Kulwant Bhogal wrote:
> 
> >> > >   dd if=/dev/sdb of=rdb.dump bs=4k count=xxx
> >> > 
> >> > > Set `xxx' such that `xxx*4096' equals the number of bytes in the
> >> > > first 2 cylinders of the disk (use HdToolBox to find out the
> >> > > cylinder size). Then sent us the output of `hexdump rdb.dump'.
> >> > 
> >> > OK, because I got a count of 615 blocks per cylinder, I used 
> >> > 615*2*4096=5,038,080 as the count. So the commandline I used was:
> >> > 
> >> > # dd if=/dev/sdb of=rdb.dump bs=4k count=5038080
> >                                  ^^^^^^^^^^^^^^^^^^^
> 
> > Is the RDB really 20 gigs though? :)
> 
> Where did you get 20 Gigs from? I only followed Geert's instructions to the
> letter. He said "set 'xxx' such that 'xxx*4096' equals the number of bytes
> in the first two cylinders of the disk and to use HDToolbox to find out the
> cylinder size. 
> 
> So, I got a cylinder size of 615 blocks per cylinder from HDToolbox, I know that there
> are 4096 bytes per block and I am supposed to dump the first two cylinders,
> I get 615*2*4096 which equals 5038080. Which is just over 4.8Mb.

You made a mistake:

	x * 4096 = 5038080

<=>	x = 5038080 / 4096

<=>	x = 1230

So you should try dd if=/dev/sdb of=rdb.dump bs=4k count=1230 .

> And this also makes sense because there are 2067 cylinders total on 
> the disk so 5038080/2 (because that was for two cylinders) * 2067 = 
> 5206855680 bytes which = 4965.64Mb or 4.849Gb - which is the size of 
> the disk.

No wonder then that trying to read around 20 GB from the disk failed. :)


-- 
Earthling Michel Dänzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member   /  CS student, Free Software enthusiast