[CentOS] unofficial ext3 and ext4 compare

I have something like 300G I routinely backup.
This includes some large 12Gig images and other files.

I had been using ext3 on an external USB disk for part of the process.

Under ext3 doing "rsync -a /home /mnt/external_back/backup.jun.27.2011"
it took 200 minutes.

I took the same computer, same external HD and reformatted it for ext4 
(mkfs.ext4 /dev/sdd1).
I then started the same rsync as above. The time was reduced to 170 minutes.

This is on Centos 5.6 x86_64.

I did notice the [ext4-dio-unwrit] process that starts up. One process 
for each core.
I was concerned when they did not go away. But google says that is 
normal. :)

Jerry