[SOLVED] disk capacity vanished

drManhattan · 03-28-2011, 05:25 PM

Hi

I partitioned my new hdd in the following scheme.

Code:

Disk /dev/sdb: 120.0 GB, 120034123776 bytes
240 heads, 63 sectors/track, 15505 cylinders
Units = cylinders of 15120 * 512 = 7741440 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xf099f099

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       15505   117217768+  83  Linux

When I perform 'df -h' it shows the following :

Code:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sdb1             111G  188M  105G   1% /media/4369cb28-c94e-4218-97b8-4c2929827f43

Why 'df -h' shows Size 111G when 'fdisk -l' shows 120 GB ?
What happened to 9 GB of space ?

thx for help.

tommylovell · 03-28-2011, 05:55 PM

Well, to start with the 120GB is the disk manufacturer's fraudulent drive size that is a "decimalized" value (they all do it).
120034123776 / (1000*1000*1000) = 120.034123776GB.

But the other value is the same number shown as a "power of two" value (i.e. 1K = 1024; 1M =1024*1024 or 1048576; 1G =1024*1024*1024 or 1073741824).
120034123776 / (1024*1024*1024) = 111.790489196777344GB.

And then there is a certain amount of overhead to any filesystem for inodes, directories, unusable starting addresses or ending addresses of partitions because of alignment. And other stuff I'm ignorant of.

chrism01 · 03-28-2011, 06:38 PM

Alsop, the default is for the system to reserve (5% iirc) for private use by the system/root in case the user area fills up and/or keeping partition defragged ie temp storage for moving blocks around.
http://linux.die.net/man/8/tune2fs