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RE: EXT3 Worries

Quoting "IT3 Stuart B. Tener, USNR-R" 
<stuart bh90210 net>:

> Recently I converted a ReiserFS partition back to 
ext2 so it could be
> resized. I then needed to convert it back to 
ReiserFS. Don't ask why, but
> it had to be done that way. Running ext3 will avoid 
this situation,
> however, it seems that 3.1GB of files on a ReiserFS 
partition, took up
> 3.6GB on an ext2 partition. Why? Does ext3 suffer 
from this deficiency? Can
> it be corrected? Obviously my files didn't change 
size when they were
> moved! What's up with that?

Well as far as ext{2|3} goes, they use inodes as part 
of the filesystem. Each file gets at least one inode.
When you format a partition with ext2/3 you can choose 
the block size (typically 1, 2, or 4k blocks) and there 
is one inode per block. If for example, you used 4k 
blocks but stored mostly 1k files, you'd be wasting 3k 
of space for each file... in fact, anytime a file 
doesn't fill space to the end of a block, you are 
throwing the rest (up to the end of the block) away.

I don't know much about ReiserFS, except that is stores 
the actual files (not just the allocation table) in a 
balanced tree structure. Having been through all the 
data structure classes of a Computer Science degree, I 
know that balanced trees are very effiecient, so I 
assume that very little space is wasted in ReiserFS.

You'll actually find that your files take up different 
ammounts of space in ALL different filesystems (the 
possible exception being ext2 and ext3 since they are 
virtually the same - except the .journal file).

Hopefully that wasn't all BS. Someone please correct me 
if I'm wrong (I'm sure you will, too :), but I hope 
that helps answer your question.

-- Mark
University - a box of academia nuts.

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