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Re: 2GB of Waste? How can it be?



Hi,

On Mon, Feb 04, 2002 at 10:40:47AM -0800, IT3 Stuart Blake Tener, USNR-R wrote:
 
> 	Why cannot ext2/ext3 allocate inode space on a dynamic basis?

It's a fundamental design property inherited from the typical Unix
filesystems which existed at the time ext2 was designed.  There are
some parts of Unix semantics which actually make it very hard to
design a filesystem in a different way (reiserfs people will tell you
just how painful it is to have to support NFS if you have dynamically
allocated inodes.)

> 	More importantly why is it not possible to amend the number of
> inodes an ext2/ext3 filesystem has after the point of doing an mke2fs?

The whole way in which inode numbers get mapped to a disk block relies
on static allocation.  We're looking at ways to do dynamic allocation,
but it is *highly* non-trivial to do so in a backwards-compatible
manner.

> 	I modified my RedHat installation to boot up using a root
> filesystem of ReiserFS, but when I try to use devfs=mount along with an
> initrd, it seems to give me some errors (initrd= something or other
> error, I will write it down next time). Any ideas?

Not without the error, no!

> 	What command do I give to tune2fs to change the space
> reservation percentage?

"man tune2fs"

> 	Also, I noticed that if I turn on ext3 journaling, I can no
> longer resize the partition with partition magic. So I am curious, how I
> can completely revert an ext3 partition back to ext2 (temporarily) so I
> can resize it, and then make it ext3 again. Is there a command line
> parameter for tune2fs which will reverse a "tune2fs -j"?

Yes -- "tune2fs -O ^has_journal" will clear the journal flag, and then
"e2fsck" will clean up the other bits that need to be cleared.

Cheers,
 Stephen





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