DF command: 12GB of memory's missing!

C-RAF. · 01-16-2006, 05:11 AM

hi,

This is weird but since one month when I use the df command on my webserver, there's 12 GB missing on a specific partition.

here is the output of df -h:

Filesystem Size Used Avail Use% Mounted on
/dev/md1 228G 211G 5.0G 98% /

I don't get it.. 211G+5G ain't giving me 228G. What the hell is going on? Where are the missing 12Gs?

If u have an idea about this one... would be great!

scuzzman · 01-16-2006, 05:36 AM

Could you please post the output of

Code:

fdisk -l

This way we can take a look at your partition setup. The output of

Code:

cat /etc/fstab

may be useful as well.

C-RAF. · 01-16-2006, 05:42 AM

ok, here it is:

fdisk -l

Quote:

Disk /dev/sda: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 146 1172713+ 83 Linux
/dev/sda2 147 268 979965 fd Linux raid autodetect
/dev/sda3 * 269 30401 242043322+ fd Linux raid autodetect

Disk /dev/sdb: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 146 1172713+ 83 Linux
/dev/sdb2 147 268 979965 fd Linux raid autodetect
/dev/sdb3 * 269 30401 242043322+ fd Linux raid autodetect

and for cat /etc/fstab:

Quote:

# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
/dev/md1 / ext3 errors=remount-ro 0 1
/dev/md0 none swap sw 0 0
proc /proc proc defaults 0 0
/dev/fd0 /floppy auto user,noauto 0 0
/dev/cdrom /cdrom iso9660 ro,user,noauto 0 0

C-RAF. · 01-16-2006, 05:44 AM

what's the "errors=remount-ro" thing in the cat output?

trickykid · 01-16-2006, 05:47 AM

Space is reserved for root and don't forgot inode's and all the other good stuff..

Example: I have a 123.5 GB drive in one of my servers, this is the output of fdisk -l:

Code:

Disk /dev/hdb: 123.5 GB, 123522416640 bytes
16 heads, 63 sectors/track, 239340 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdb1               1      239340   120627328+  83  Linux

And this is the output of df -h:

Code:

Filesystem            Size  Used Avail Use% Mounted on
/dev/hdb1             114G   35G   74G  32% /data

This is totally normal behavior.. even if you have a 300GB drive in Windows and you format it as NTFS, the drive will end up being 279GB usable space available.

C-RAF. · 01-16-2006, 05:56 AM

Quote:

Originally Posted by trickykid

Space is reserved for root and don't forgot inode's and all the other good stuff..

Yeah I know... but since I got this space one month ago... I still don't understand. (I mean, 12gb for inodes???

)

C-RAF. · 01-16-2006, 06:01 AM

Quote:

Originally Posted by trickykid

This is totally normal behavior.. even if you have a 300GB drive in Windows and you format it as NTFS, the drive will end up being 279GB usable space available.

Aiight, I get the point... that's why there's 228GB of the 250GB disk in the DF command output, BUT that doesn't explain why I can't use 12GB within these 228GB?

C-RAF. · 01-16-2006, 06:09 AM

Quote:

Originally Posted by C-RAF.

what's the "errors=remount-ro" thing in the cat output?

humm, it seems to be normal:

http://lists.debian.org/debian-devel.../msg02267.html

okay... I really don't get it.

michaelk · 01-16-2006, 06:39 AM

Quote:

BUT that doesn't explain why I can't use 12GB within these 228GB?

Like trickykid posted. An ext2/ext3 file system by default reserves 5% for roots use. This is supposed to reduce fragmentation and allow root to access the filesystem to perform maintenance in case it becomes full. (228 * .05 = 11.4GB)

You can tune2fs to reduce the amount of reserved space.

Wim Sturkenboom · 01-16-2006, 07:09 AM

Quote:

Originally Posted by C-RAF.

Aiight, I get the point... that's why there's 228GB of the 250GB disk in the DF command output

No, that's because a kilobyte is not a kilobyte. HD manufacturers specify HDs in such a way that 1000 bytes is 1kB, but computers calculate with 1024 bytes for 1kB.
The real size of your HD = 250*1000*1000*1000/(1024*1024*1024) = 232GB.

C-RAF. · 01-16-2006, 07:21 AM

Okay, that stuff confused & is still confusing me. This is crazy that I just can use 216GB on a 250GB disk

.

My co-worker was saying that one month ago he was sure that we could use the 228GB.
Me too, I don't remember this hole when reading the df output.

that's w.e.i.r.d

anyway, thx for your answers guyz!