Virtual machines installation
The first benchmark consisted in a timed, concurrent installation of four virtual machines. I used PXE to boot the VMs, a CentOS-7.0-1406-x86_64-Minimal.iso image connected as an IDE cd-rom as the installation disk, and a FTP-provided kickstart file for unattended installation.
Interesting, it isn't? ZFS was the absolute leader, with the various logical volumes configurations somewhat left behind. I attribute this great show to ZFS Intent Log (ZIL), but I can be wrong. At the third place we see a group including XFS, EXT4 and Qcow2 native images. At the very last place we see BTRFS, which remains slow even when disabling its CoW behavior.
If you think that installation time is a relatively unimportant operation and that BTRFS may fare well in the real benchmark, well, go ahead...