Re: tlug: Sun disk label fdisk/SCSI question

[Rex Walters <rex@example.com>]

On Tue, Jun 09, 1998 at 11:38:42AM +0900, Tim Meggs wrote:
> 
> Just went to install a new HD into my IPC box.    
> 
> When creating a new Sun disk label for the HD using fdisk [the 'auto detect'
> option wouldn't detect it] the 'hardware detected' defaults suggested by fdisk 
> in 'custom' mode don't correspond the the physical properties of the disk.

"Physical properties of the disk" you probably don't want to know.

The number of cylinders/heads/sectors is pretty much meaningless with
SCSI.  You can set it to anything you want -- many modern disks have
constant arial density rather than constant linear density anyway (more
sectors on the outside).  The device drivers use c/h/s as for
anachronistic backward compatibility reasons.  

SCSI puts a lot of intelligence at the disk.  The controller just says
gimme block n and the disk is responsible for figuring out the physical
geometry translation.

The common practice these days is to use 64 heads, 32 sectors per track
(1 MB per cylinder).  Then just set the number of cylinders to the size
of your disk.  Many disk manufacturers put some sort of label on the
outside of their disks specifying the total number of 512 byte sectors).
Divide by two and you've got the number of cylinders to specify.  DON'T
change the label (h/s) if you've got data you want to keep on the disk,
of course.

The "Large-Disk" howto is pretty good reading
(/usr/doc/HOWTO/mini/Large-Disk) on a redhat box.

SCSI and NFS I grok.  The i18n stuff flying on this list is *WAY* over
my head....

Cheers,
-- 
Rex
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