Currently the Build Appliance root FS is Ext3. Switching to Ext4 will bring it more in-line with other BSPs. There are some additional benefits for Ext4 when used in combination with .VDI image.
Posted patches to openembedded-core@lists.openembedded.org for a review
Merged https://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=7cc816b9ffefd5debb23bfb7ba66a7dc8e0ac94d
verified with build 1.9 M3 rc1