Ext2 and ext4 preallocation / mballoc

Ext2 and ext4 preallocation / mballoc

[Gaëtan Podevijn]

Hello,

Reading this http://web.mit.edu/tytso/www/linux/ext2intro.html I
understand that ext2 preallocates 8 blocks when a writing data to a
file. Ext3 uses the windows reservations method, but is that ext3 also
preallocates 8 blocks when writing data ?

Moreover, this page
http://kernelnewbies.org/Ext4#head-b2148d2a96d22a1bd7e376e6c08e4a38d08fb157
explains that ext3 allocates one block at a time and ext4 uses
multiblock allocation that is, allocates many block in a single system
call.

What is the difference between preallocation on ext2 (and ext3 ?) and mballoc ?


TYA,

Gaëtan

PS : I'm sorry for my really bad english
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Re: Ext2 and ext4 preallocation / mballoc

[Aneesh Kumar K. V]

On Wed, 17 Feb 2010 16:46:19 +0100, Gaëtan Podevijn <gpodevij@gmail.com> wrote:
> Hello,
> 
> Reading this http://web.mit.edu/tytso/www/linux/ext2intro.html I
> understand that ext2 preallocates 8 blocks when a writing data to a
> file. Ext3 uses the windows reservations method, but is that ext3 also
> preallocates 8 blocks when writing data ?
> 
> Moreover, this page
> http://kernelnewbies.org/Ext4#head-b2148d2a96d22a1bd7e376e6c08e4a38d08fb157
> explains that ext3 allocates one block at a time and ext4 uses
> multiblock allocation that is, allocates many block in a single system
> call.
> 
> What is the difference between preallocation on ext2 (and ext3 ?) and mballoc ?
> 
> 


You can find mballoc details at 

http://ols.fedoraproject.org/OLS/Reprints-2008/kumar-reprint.pdf

-aneesh
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