Do we need dump for ext4?

[Eric Sandeen <sandeen@redhat.com>]

I was talking to Ric about dump benchmarks, and he was of the impression
that dump may not be used that often anymore, at least in the
enterprise.  (Ric, hope I'm paraphrasing correctly)

Undaunted :) I ran off and tested an artificial backup scenario:

* Untar a kernel tree into 128 different top level dirs
* Make a level 0 backup
* Untar a kernel tree into 128 MORE different top level dirs
* Make a level 1 backup

128 kernel trees uses about 6.5M inodes, and about 80G of space.

I tested ext3 with dump; ext4 with tar, and xfs with xfsdump.

for ext3:
dump -1 -u -f $DUMPDIR/dump1 $DATADIR

for ext4:
tar --atime-preserve --xattr --after-date=$DUMPDIR/dump0.tar -cf
$DUMPDIR/dump1.tar $DATADIR

for xfs:
xfsdump -F -l 1 -f $DUMPDIR/dump0 $DATADIR

DUMPDIR and DATADIR were 2 partitions on the same (fast hardware) lun.

Results:

	level0	level1
        ------	------
ext3	38m52s	42m21s
ext4	57m55s	69m35s
xfs	25m18s	37m44s

Clearly tar on ext4, at least for my incantation, lags.  Is dump for
ext4 anywhere on the todo list, or should it be?  Or am I just running
tar wrong? :)

-Eric