---
other:
  - |
    Nova now has a config option called
    ``[workarounds]/never_download_image_if_on_rbd`` which helps to
    avoid pathological storage behavior with multiple ceph clusters.
    Currently, Nova does *not* support multiple ceph clusters
    properly, but Glance can be configured with them. If an instance
    is booted from an image residing in a ceph cluster other than the
    one Nova knows about, it will silently download it from Glance and
    re-upload the image to the local ceph privately for that
    instance. Unlike the behavior you expect when configuring Nova and
    Glance for ceph, Nova will continue to do this over and over for
    the same image when subsequent instances are booted, consuming a
    large amount of storage unexpectedly. The new workaround option
    will cause Nova to refuse to do this download/upload behavior and
    instead fail the instance boot. It is simply a stop-gap effort to
    allow unsupported deployments with multiple ceph clusters from
    silently consuming large amounts of disk space.
