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



Dr. Tweedie, et al.:

	In the instant case, I am creating a filesystem for /home
directories, thus, a 5% reservation for root is not needed here, so I
shall take your advice and return it to the general free space pool.

	Why cannot ext2/ext3 allocate inode space on a dynamic basis?

	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?

	One other question, as well:

	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?

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

	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"?


Very Respectfully, 

Stuart Blake Tener, IT3 (E-4), USNR-R, N3GWG 
Beverly Hills, California
VTU 1904G (Volunteer Training Unit) 
stuart bh90210 net 
west coast: (310)-358-0202 P.O. Box 16043, Beverly Hills, CA 90209-2043 
east coast: (215)-338-6005 P.O. Box 45859, Philadelphia, PA 19149-5859 

Telecopier: (419)-715-6073 fax to email gateway via www.efax.com (it's
free!) 

JOIN THE US NAVY RESERVE, SERVE YOUR COUNTRY, AND BENEFIT FROM IT ALL. 

Sunday, January 13, 2002 4:38 AM


-----Original Message-----
From: Stephen C. Tweedie [mailto:sct redhat com] 
Sent: Monday, February 04, 2002 10:19 AM
To: IT3 Stuart Blake Tener, USNR-R
Cc: ext3-users redhat com
Subject: Re: 2GB of Waste? How can it be?

Hi,

On Mon, Feb 04, 2002 at 10:05:48AM -0800, IT3 Stuart Blake Tener, USNR-R
wrote:
> Dr. Tweedie, et al.:
> 
> 	I recently formatted a partition using EXT3, and after a "df -h"
> I get 14GB of space. When I reformatted the partition with ReiserFS,
and
> did a "df -h" I got 16GB of space!

ext3 uses exactly the same rules as ext2 here.  By default, 5% of the
filesystem is "reserved" for root --- tune2fs can modify that.  There
is also the fact that ext2 and ext3 preallocate space for inodes: if
you expect only to have a few large files, "mke2fs -i" can be used to
reduce the amount of inode space preallocated.

> 	Now the partition was setup to be 16GB via fdisk, so 16GB is
> correct. However, why does EXT3 loose 2GB of space? 

It doesn't --- the space is just reserved, either for root access or
for the inode data structures.  reiserfs also needs space for data
structures analagous to inodes, but it allocates that space
dynamically so you don't see it on a newly-created filesystem.

> The journals cannot
> be that big!?!

No, they should only be a few tens of MB at most.

Cheers,
 Stephen





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