Re: Disk Space Calculation - Some Space missing - Where did it Go?
On Fri, 2007-04-06 at 13:40 -0700, Andrew Sackville-West wrote:
> On Fri, Apr 06, 2007 at 11:26:46PM +0530, Siju George wrote:
> > Hi,
> >
> > Just want to know a little bit about disk space calculation.
> >
> > I have a hard disk of 500 GB as shown here.
> >
> > =============================================================================
> > websrv-1:~# fdisk -l /dev/sda
> >
> > Disk /dev/sda: 500.1 GB, 500106813440 bytes
> [...]
> > There are 3 partitions
> >
> > 1) sda5 is LVM and is 464 GB approx
> [...]
> > 2) sda1 and sda2 are 300MB and 2GB approximately.
> [..]
> > So sda5 + sda1 + sda2 = 470GB + 300MB + 2 GB = 472.3 or 473GB approximately.
> >
> > But my hard disk is 500GB.
> >
> > So where did 27 ( 500 -473 ) GB go?
> >
> > Is there any error in my Calculations?
>
> disk drive manufacturers label their disks based on a 1 GB = 1000 MB =
> 1000 K, but the partition sizes are based on 1 GB = 1024 MB = 1024 K.
>
> that's how I understand it.
That is how the user is bamboozled. Even the drive itself says it right
on its label, after a few lawsuits.
I just happen to have 4 - 300GB disks in a single LVM volume group.
# vgdisplay voidVG
--- Volume group ---
VG Name voidVG
Format lvm2
[snip]
VG Size 1.09 TB
PE Size 32.00 MB
Total PE 35772
Each one of those drives is a "300GB" drive. But yet, I only get 1.09TB
out of the 4 drives.
Now, lets try the math to explain this. We should have 1200G or 1.2T.
But wait we actually do.
Figure it this way:
35775 (number of Physical Extents)
x 32 MB Physical Extent size
x 1024 KBytes per MByte
x 1024 Bytes per KByte
-----------------------------------
1,200,409,804,800 Bytes
Are we clear yet? See it *DOES* == 1.2T (base10)
--
greg, greg@gregfolkert.net
Novell's Directory Services is a competitive product to Microsoft's
Active Directory in much the same way that the Saturn V is a competitive
product to those dinky little model rockets that kids light off down at
the playfield. -- Thane Walkup
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