.. dnn1552678684527 .. _storage-functions-osds-and-ssd-backed-journals: =============================================== Storage Functions: OSDs and SSD-backed Journals =============================================== Disks on storage hosts are assigned storage functions in |prod| to provide either OSD storage or Ceph journal storage. Rotational disks on storage hosts are always assigned as object storage devices (OSDs) to provide storage for Application disks. Solid-state disks \(SSDs) can be assigned as OSDs, or as journal functions to provide space for Ceph transaction journals associated with OSDs. NVMe-compatible SSDs are also supported. To assign storage-host disks as OSDs, see :ref:`Provision Storage on a Controller or Storage Host Using Horizon `. To create SSD-backed journals, see :ref:`Add SSD-Backed Journals Using Horizon `.