regular fsck runs are too disturbing - and current approach does not work very well in detecting defects!

Jan Claeys lists at
Tue Oct 9 02:54:23 UTC 2007

Op maandag 08-10-2007 om 13:16 uur [tijdzone -0400], schreef Phillip
> Jan Claeys wrote:
> > But I think a similar API could be used to mark & move bad sectors or
> > "lost" sectors, and that's more related to this discussion...
> As I said, there is no need to make such an effort because ext rarely 
> becomes fragmented enough to worry about.  The fact that the defrag 
> package has not really been maintained in 10 years shows that there is 
> no strong need for an offline defrag, let alone an online one.

The main reason (IMO) why "defrag" is not useful (anymore) is that for
ages there hasn't been any (guaranteed) correlation between hardware
order and software order of sectors on a disk.  Defragmenting disks
might actually fragment them more on a fysical level, and thus cause
slow-downs.  And in some cases (fysically) fragmented sectors might be
faster to read/write than non-fragmented ones (I used a custom,
partially self-written, diskette formatting program to do exactly that
under MS-DOS!).  So, any defrag program would require help from the hard
disk's firmware to be really efficient (and AFAIK no firmware supports

But, what I was thinking about was similar atomic operations that allow
_other_ filesystem cleaning tasks to be done while a filesystem is in
use (r/w).  ('fsck' might be an example.)

I understand these don't exist now, but they might be a good idea for
future filesystems or filesystem versions...  :)

Jan Claeys

More information about the Ubuntu-devel-discuss mailing list