In previous lustre versions, when creating ldiskfs OSTs, the default
mount options were "errors=remount-ro,extents,mballoc". Somewhere along
the way (lustre 2.5.1?) the mount options changed to "errors=remount-ro".
I suspect the change is because mballoc & extents are now defaults of
the underlying ext4 filesystem.
FYI Section 33 of lustre admin guide documents the ldiskfs persistent
mount options for commands "mkfs.lustre" & "tunefs.lustre" but the
in these two places are different. YMMV.
yale hpc group