cpio to ext4 seems much slower than to ext2, ext3 or xfs

[Richard W.M. Jones]

On Thu, Nov 12, 2009 at 09:54:12AM +0000, Daniel P. Berrange wrote:
> On Wed, Nov 11, 2009 at 09:05:20PM +0000, Richard W.M. Jones wrote:
> > On Wed, Nov 11, 2009 at 01:24:20PM -0600, Eric Sandeen wrote:
> > > Anybody got actual numbers?  I don't disagree that mkfs.ext4 is slow in  
> > > the default config, but I don't think it should be slower than mkfs.ext3  
> > > for the same sized disks.
> > 
> > Easy with guestfish:
> > 
> >   $ guestfish --version
> >   guestfish 1.0.78
> >   $ for fs in ext2 ext3 ext4 xfs jfs ; do guestfish sparse /tmp/test.img 10G : run : echo $fs : sfdiskM /dev/sda , : time mkfs $fs /dev/sda1 ; done
> >   ext2
> >   elapsed time: 5.21 seconds
> >   ext3
> >   elapsed time: 7.87 seconds
> >   ext4
> >   elapsed time: 6.10 seconds
> >   xfs
> >   elapsed time: 0.45 seconds
> >   jfs
> >   elapsed time: 0.78 seconds
> > 
> > Note that because this is using a sparsely allocated disk each write
> > to the virtual disk is very slow.  Change 'sparse' to 'alloc' to test
> > this with a non-sparse file-backed disk.
> 
> You really want to avoid using sparse files at all when doing any kind of
> benchmark / performance tests in VMs. The combo of a sparse file store on
> a journalling filesystem in the host, w/ virt can cause very pathelogically
> bad I/O performance until the file has all its extents fully allocated on
> the host FS. So the use of a sparse file may well be exagarating the real
> difference in elapsed time between these different mkfs calls in the 
> guest.

Again, this time backed by a 10 GB logical volume in the host, so this
should remove pretty much all host effects:

$ for fs in ext2 ext3 ext4 xfs jfs reiserfs nilfs2 ntfs msdos btrfs hfs hfsplus gfs gfs2 ; do guestfish add /dev/mapper/vg_trick-Temp : run : zero /dev/sda : echo $fs : sfdiskM /dev/sda , : time mkfs $fs /dev/sda1 ; doneext2
elapsed time: 3.48 seconds
ext3
elapsed time: 5.45 seconds
ext4
elapsed time: 5.19 seconds
xfs
elapsed time: 0.35 seconds
jfs
elapsed time: 0.66 seconds
reiserfs
elapsed time: 0.73 seconds
nilfs2
elapsed time: 0.19 seconds
ntfs
elapsed time: 2.33 seconds
msdos
elapsed time: 0.29 seconds
btrfs
elapsed time: 0.16 seconds
hfs
elapsed time: 0.44 seconds
hfsplus
elapsed time: 0.46 seconds
gfs
elapsed time: 1.60 seconds
gfs2
elapsed time: 3.98 seconds

I'd like to repeat my proviso: I think this test is meaningless for
most users.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
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