I did 4 clean installations of debian 6 and measured time of installing some average virtual package. FS options are default.
time apt-get install build-essential
I got very strange results (min:sec, less is faster):
XFS: 3:12 btrfs: 2:45 ext3: 0:30 ext4: 0:50
What the flying flock wrong with the first two? 6 times slower than ext3? Am I doing something wrong?
Upd (some details):
All LVM volumes are local to VM and are on idle RAID. CDROM image is local and the same, Internet connection is stable and it factors max 10-15 seconds. All the visible slowdowns are after downloads: XFS and btrfs guests think over 1 second every
Unpacking. Low-level caching is disabled. Host node is idle every installation, no active guests but the one.