ext3 real disk occupation of a file

Eric Sandeen sandeen at redhat.com
Tue Aug 18 18:05:42 UTC 2009

Youness HAFFANE wrote:
> Hi Eric,
> I have understood from the document, that for each file, we have 3 extra
> blocks (indirect) that refer to  :
> - the group descriptor
> - the block bitmap
> - the inode bitmap
> Is that right?

nope :)

> If not, to what the indirect blocks refer to? and are there always only
> 3 blocks for each file in ext2/3fs?

No.  basically the extra blocks are for keeping track of where the data
blocks are, or for keeping track of where more indirect blocks are,
which in turn keep track of where the data blocks are.

Maybe http://www.nongnu.org/ext2-doc/ext2.html#DEF-INODES has a better

"There are pointers to the first 12 blocks which contain the file's data
in the inode. There is a pointer to an indirect block (which contains
pointers to the next set of blocks), a pointer to a doubly-indirect
block (which contains pointers to indirect blocks) and a pointer to a
trebly-indirect block (which contains pointers to doubly-indirect blocks). "

It's all these indirect blocks that you're seeing.


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