IDE Device Space Question?

kushalkoolwal · 11-04-2005, 12:57 PM

I have an IDE device of 512MB(unformatted). I created a single partition and formatted it with ext3 filesystem. Now I mounted that device on /mnt/test directory. Now when I give the command df -h to check the total space on the device it shows something like this:

Code:

root@debian:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda7             7.5G  4.4G  2.7G  63% /
tmpfs                 629M     0  629M   0% /dev/shm
/dev/hdc1             482M  8.1M  449M   2% /mnt/debian
root@debian:~#

The total size if 482MB which is ok. But why the available space is 449MB only inspite when it shows that used space is just 8.1MB? Ideally it should be 475MB or somewhere around that.

Anyone has any Ideas as to why this is happening?

thanks

michaelk · 11-04-2005, 01:40 PM

By default when you format an ext2/3 filesystem 5% of the space is reserved for root.
Reserved space is supposed to reduce fragementation as well as allow root to login in case the filesystem becomes full. On a data drive you can get away with 1% or even zero.

Use tune2fs to modify the amount of reserved space.

kushalkoolwal · 11-04-2005, 02:28 PM

Thanks that was good to know. Thanks a lot man.

Wells · 11-04-2005, 03:26 PM

Also, if there is no data on the drive, you can always reformat the drive and use the -m option of mkfs.ext3:

Code:

       -m reserved-blocks-percentage
              Specify the percentage of the filesystem blocks reserved for the super-user.  This avoids fragmentation, and allows root-owned  daemons,  such
              as  syslogd(8),  to  continue  to function correctly after non-privileged processes are prevented from writing to the filesystem.  The default
              percentage is 5%.