Re: Does "32.1% non-contiguous" mean severely fragmented?

[Theodore Tso <tytso@mit.edu>]

On Mon, Oct 22, 2007 at 08:58:11PM +0900, Tetsuo Handa wrote:
> 
> --- Start VM ---
> --- Suspend VM ---
> [root@sakura Ubuntu7.10]# filefrag Ubuntu7.10.vmem
> Ubuntu7.10.vmem: 751 extents found, perfection would be 5 extents
> [root@sakura Ubuntu7.10]# sync
> [root@sakura Ubuntu7.10]# filefrag Ubuntu7.10.vmem
> Ubuntu7.10.vmem: 3281 extents found, perfection would be 5 extents
> [root@sakura Ubuntu7.10]# filefrag Ubuntu7.10.vmem
> Ubuntu7.10.vmem: 3281 extents found, perfection would be 5 extents
> --- Resume and poweroff VM ---
> 
> What? "sync" yields more discontiguous?

What filesystem are you using?  ext3?  ext4?  xfs?  And are you using
any non-standard patches, such as some of the delayed allocation
patches that have been floating around?  If you're using ext3, that
shouldn't be happening.....

If you use the -v option to filefrag, both before and after the sync,
that might show us what is going on.  The other thing is to use
debugfs and its "stat" command to get detailed breakdown of the block
assignments of the file.

Are you sure the file isn't getting written by some background tasks
that you weren't aware of?  This seems very strange; what
virtualization software are you using?  VMware, Xen, KVM?

	       		    			     - Ted