disk_config vda
primary   -          20GiB   -      -
primary   -           4GiB   -      -

disk_config vdb
primary   -          20GiB   -      -
primary   -           4GiB   -      -

disk_config raid
raid1     /      vda1,vdb1   ext3   rw
raid1     swap   vda2,vdb2   swap   sw