We add the disks key as in the following example:

  "nodes": {
    ...
  },
  "disks": {
    sdb.grimoire-1.nancy.grid5000.fr": {
      "diskpath": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:0:1:0"
      "soft": free/busy (depending if the disk is free or not)
      "reservations": [...] (the jobs which reserved that disk)
    }
  }