ldiskfsck | statically-linked lustre version of the ext2 filesystem checker | Mehr ...
This binary is necessary in order to check the lustre filesystem on OST and MGS nodes. This binary is linked statically in order to do not conflict with the regular e2fsck package, therefore it will consume much more space thant it's dynamic linked counterpart.
lfsck | statically linked version of the lustre filesystem checker | Mehr ...
This binary is necessary to check the complete lustre filesystem for errors. You only need that package on lustre clients.