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

[Kulwant B. <kul...@bt...>]

Hello Michel,

>> > >   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. 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. 

There are 1271205 blocks on the disk and 1271205*4096 also = 4.8Gb. 

The thing that puzzles me is that the Seagate specs for the drive
(http://www.seagate.com/support/disc/specs/scsi/st34573lc.html) (lw [mine] is also
on this page) bear no resemblance to the HDToolbox numbers even after
accounting for the 4096 blocksize. Examples are number of tracks: 37,505,
cylinders: 7,501, heads physical: 5, disks (3.5 inch): 3. 
The number of sectors is not too far out at 8,888,924 (/8 = 1,111,116). 
(Seagate numbers). 
 
HDToolbox states that there are 3 heads. 

I suspect that HDToolbox does it's own interpretation of the drive geometry
- which also happens to work (somehow!!). Actually I am surprised that it
actually all works - well it works as long as you don't want to reformat to a foreign
(to AmigaOS) disk format!. 

But for Linux, I am not sure where that leaves us. 

Kind regards, 

Kulwant