Re: mke2fs & capacity (where did it go!?)
Hmmm interesting !
Thanks.
On Mon, 15 Dec 1997, David Wright wrote:
> On Mon, 15 Dec 1997, matthew tebbens wrote:
>
> > On Mon, 15 Dec 1997, David Wright wrote:
> >
> > > On Sun, 14 Dec 1997, matthew tebbens wrote:
> > >
> > > > (victor)[root:~#] mke2fs -c -v /dev/sda1
> > > > mke2fs 1.10, 24-Apr-97 for EXT2 FS 0.5b, 95/08/09
> > > > Linux ext2 filesystem format
> > > > Filesystem label=
> > > > 1101824 inodes, 4401778 blocks
> > > > 220088 blocks (5.00%) reserved for the super user
> > > > First data block=1
> > > > Block size=1024 (log=0)
> > > > Fragment size=1024 (log=0)
> > > > 538 block groups
> > > > 8192 blocks per group, 8192 fragments per group
> > > > 2048 inodes per group
> > > > Superblock backups stored on blocks:
> [...]
> > > > What am I missing here ??
> > >
> > > 4,033,188 + 220,088 + 13 = 4,253,289 so that's all right then.
> > > But that's not what's at issue.
> > > What's relevant is the 4,401,778 blocks which becomes 4,507,420,672 bytes.
> > > That looks better. But even that is only looking at the first partition
> > > (sda1, sdb1 etc.)
> >
> > But I don't have 4,401,778 blocks, I only have a total of 4,253,289 blocks
> > which becomes aprox 4,355,367,000 bytes.
> >
> > How does it get from 4,401,778 blocks to 4,253,289 blocks ?
> > Somewhere along the line I lost about 250,000 blocks... ??
>
> The partition has 4,401,778 blocks in total. There are 4,253,289 blocks
> available for your data. Somewhere, the filesystem has to describe where
> all that data is.
>
> Your filesystem has 1,101,824 inodes and, taking a quick look at
> /usr/src/linux/include/linux/ext2_fs_i.h which describes inodes in
> memory, there seem to be about 112 bytes in an inode. That adds up to
> about half your "missing" space. But there's more to describing the
> filesystem than just the inodes, and ext2 is optimised for performance,
> which must mean using more space for chains of descriptors etc.. Perhaps you
> should read a book on linux internals to find out what you're missing.
> (Sorry for the pun.)
>
> --
> David Wright, Open University, Earth Science Department, Milton Keynes MK7 6AA
> U.K. email: d.wright@open.ac.uk tel: +44 1908 653 739 fax: +44 1908 655 151
>
>
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