Intel(r) Core?2 Duo Processors"

[Jay Cliburn]

Tony Nelson wrote:
> At 12:28 AM +0200 10/13/06, Dotan Cohen wrote:

>> How can I check fragmentation. Googling the subject makes me beleive
>> that this is not the case in general with Linux.
> 
> The common wisdom is that EXT2/3 are not affected by fragmentation, but
> without much real-world proof that this is so.  The EXT2/3 filesystem
> metadata was designed to be not much affected by fragmentation, but that
> says little about the file data.  I read an article / webpage (that I can't
> find right now) by someone who decided to experiment with new and used EXT2
> filesystems, and found a substatial slowdown.  He was inspired to try this
> because he noticed that his computer sped up when given a fresh filesystem.
> You could try backing up and restoring to a fresh filesystem.  If you
> spring for a new computer you'll back up and restore to the new computer.
> Either way you'll get a fresh new filesystem.

We've seen significant I/O slowdown on a 4,176-processor Cray XT3 because of 
file fragmentation on an ext3 filesystem (overlaid with Lustre).  Admittedly the 
filesystem in question was about 40 terabytes in size and running under a 2.4 
kernel, but fragmentation was there nonetheless.  We solved the problem by 
rebuilding the filesystem.

See here for a related reference that speaks to improvements in ext3 block 
allocation for 2.6.10+ kernels: 
http://ext2.sourceforge.net/2005-ols/paper-html/node7.html