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Old 03-28-2011, 05:25 PM   #1
Registered: Aug 2010
Location: Warsaw, Poland
Distribution: Ubuntu 10.04 LTS on IBM Lenovo R61e, RHEL5-6,SLES10-11
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disk capacity vanished


I partitioned my new hdd in the following scheme.
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 :
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.
Old 03-28-2011, 05:55 PM   #2
Registered: Nov 2005
Distribution: Fedora, Redhat
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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.

Last edited by tommylovell; 03-28-2011 at 06:28 PM.
Old 03-28-2011, 06:38 PM   #3
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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.


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