[Q] Is this true and does it mean there is dynamic entation in ext2/3?

Damian Menscher menscher at uiuc.edu
Fri Jul 8 18:55:05 UTC 2005

[Resurrecting an ancient thread...]

On Tue, 21 Jun 2005, Markus Peuhkuri wrote:
> Theodore Ts'o wrote:
>> Ext2/3 has advanced algorithms to make sure that the blocks that are
>> allocated avoid fragmentation, but it is not doing any kind of dynamic
> And there is a tool 'filefrag' in e2fsprogs that reports how fragmented
> a particular file is.  If your disk grows full (over 90-95%, depending
> on file sizes etc..) then it is more difficult to find continuous blocks
> for files.  Now, if you delete files, then new files most probably are
> non-fragmented but those files that were written when disk was full are
> still fragmented.
> You can "unfragment" those files just by copying them and deleting old
> ones (if you have plenty of free space), but as Damian told, you must be
> careful with locks and nfs handles.

I have a user who is complaining of general slowness on his machine 
(RH9, so e2fsprogs-1.32-6).  The slowness is particularly bad when he 
types "mail" to read his email.  I can't find anything wrong with the 
system itself (no cpu load, free ram, no heavy disk activity, etc) but 
did note that when opening his mailbox (only 26M, so nothing huge) it 
does hang for 5-10 secs, apparently waiting on disk.  Running filefrag 
on his mailbox indicates it has 1119 extents.  I suspect that may be the 
source of the problem.

Now, I realize some fragmentation is normal, but I'd have expected that 
a mailbox with 328 messages wouldn't get more than 328 fragments (or 
possibly twice that many) maximum.  And the filesystem is only 42% full, 
so that's not causing extra fragmentation.

Is there anything I should be watching for here, or should I just give 
up and copy the file?

Damian Menscher
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