[ale] Seagate Hdd Not Lining Up!? -- Diverging from the problem...

[Jim Kinney]

On Sat, Jul 11, 2009 at 7:48 PM, Tim Watts <timtw at earthlink.net> wrote:

> Hi,
>
> Just out of curiosity, why doesn't the reported total bytes on the drive
> divide evenly by the bytes/cylinder? Where would those extra bytes reside
> if
> not on a cylinder? And why isn't the total == 320GB? (I suppose the answer
> to
> the last question is tied up in the bad sector map. But how do they keep
> those
> out of the usable cylinder space? Or do they?)


There are usually extra chunks of drive available to handle failing
sections. That tends to throw off the numbers a bit. The total drive amount
is in 1000 instead of 1024 units so the division gets bad. The actual space
is a  marketing  scam.

An issue I have yet to be clear on myself is does the bits/cylinder change
across the drive? The inner cylinders have less surface area than the outer
cylinders. So maybe the bits/cylinder is also synthetic...

>
>
> And OK, I'm not afraid to look totally stupid (but I'll qualify my question
> by
> saying it's been /years/ since I've stuck my head inside a drive): Am I to
> believe that these drives, which can't be more than 3/4" high, /really/
> have
> 255 platters spinning inside them with an arm between each platter? Or has
> the
> geometry all been virtualized today? If you tightly stacked 255 crisp $1
> bills, do you know how high it would be? I don't, but I'm pretty sure it'd
> be
> more than 3/4"! (BTW, if you do know, you're spending way too much time at
> the
> strip clubs.)
>

Every drive I've ever opened in the last 10 years had a single platter. I
have not opened a SAS or newer SCSI drive yet. The really high throughput
drives may actually have more platters/heads but I have yet to have the
opportunity to ruin one with a screwdriver.



>
> Thanks,
>  Tim
>  (who is awed by all this and just choc full o'questions)
>
>
> On Saturday 11 July 2009 5:28:22 pm Michael B. Trausch wrote:
> > On Sat, 11 Jul 2009, Brian Pitts wrote:
> > > Marc Ferguson wrote:
> > > > [root at fergatron ~]# fdisk -l /dev/sdb
> > >>
> > >> Disk /dev/sdb: 320.0 GB, 320072933376 bytes
> > >> 255 heads, 63 sectors/track, 38913 cylinders
> > >> Units = cylinders of 16065 * 512 = 8225280 bytes
> > >> Disk identifier: 0x0b99f72f
> > >>
> > >>    Device Boot      Start         End      Blocks   Id  System
> > >> /dev/sdb1               1       38913   312568641   83  Linux
> > >> [root at fergatron ~]#
> > >>
> > >> I'm not fully comprehending these outputs. Do they indicate anything
> of
> > >> significance?
> > >
> > > That looks like one (roughly) 320 GB partition to me. You could try to
> > > grow the filesystem by running the following as root
> > >
> > > umount /dev/sdb1
> > > e2fcsk -f /dev/sdb1
> > > resize2fs -p /dev/sdb1
> > > mount /dev/sdb1 /media/backup
> >
> > If the kernel is recent enough, and the filesystem is extXfs, it should
> be
> > growable online.
> >
> >       --- Mike
> > _______________________________________________
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> > Ale at ale.org
> > http://mail.ale.org/mailman/listinfo/ale
>
> --
> Most modern calendars mar the sweet simplicity of our lives by reminding us
> that each day that passes is the anniversary of some perfectly
> uninteresting
> event.
>  -- Oscar Wilde
>
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-- 
-- 
James P. Kinney III
Actively in pursuit of Life, Liberty and Happiness
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