Defrag.

[Dave Mitchell]

On Thu, Oct 06, 2005 at 03:31:43PM -0400, AragonX wrote:
> So what if you have the same 18k file that is stored as you said, in 2 8k
> blocks and then one 2k chunk.  Now you add more files to the system.  Next
> you add another 18k to the first file the next day.  Continue for a month.
>  You would have something that looks like this right:
> 
> 
> 11111111  11111111  11222---  22222222  22222222  3333333-  ->
> --------  --------  --------  --------  --------  -------
> 1 - 18k
> 2 - 19k
> 3 - 7k
> 
> I'm just guessing this is how the data would be written to disk.  I don't
> really know.  So on to day 2 when I add 18k to file 1, the data would be
> arranged on the drive platter as so?
> 
> 11111111  11111111  11222---  22222222  22222222  3333333-  ->
> 11111111  11111111  11------

No, only the last chunk of any file is put into a split block, ie

11111111  11111111  --222---  22222222  22222222  3333333-  ->
11111111  11111111  1111----

> So I'm still getting fragmentation, just not nearly as bad as it is on a
> FAT or NTFS machine correct?
> 
> I'm just trying to understand.  I've heard the argument that "Linux does
> not  have any fragmentation to worry about".  I just don't see how that is
> possible on a desktop machine where lots of little files are modified
> frequently.

Linux *does* have fragmentation, just not generally enough to be a
problem. There are many other mechanisms going on (like dividing the disk
into cylinder groups) that operate to keep fragmentation manageable.

(Again with the proviso that I'm most familiar with UFS).


-- 
Little fly, thy summer's play my thoughtless hand
has terminated with extreme prejudice.
        (with apologies to William Blake)