Public bug reported: Nova does not currently support multiple rbd backends. However, Glance does and an operator may point Nova at a Glance with access to multiple RBD clusters. If this happens, Nova will silently download the image from Glance, flatten it, and upload it to the local RBD cluster named privately to the image. If another instance is booted from the same image, this will happen again, using more network resources and duplicating the image on ceph for the second and subsequent instances. When configuring Nova and Glance for shared RBD, the expectation is that instances are fast-cloned from Glance base images, so this silent behavior of using a lot of storage would be highly undesirable and unexpected. Since operators control the backend config, but users upload images (and currently only to one backend), it is the users that would trigger this additional consumption of storage.
This isn't really a bug in Nova per se, since Nova does not claim to support multiple backends and is download/uploading the image in the same way it would if the image was located on any other not-the-same-as- my-RBD-cluster location. It is, however, unexpected and undesirable behavior. ** Affects: nova Importance: Undecided Status: New -- You received this bug notification because you are a member of Yahoo! Engineering Team, which is subscribed to OpenStack Compute (nova). https://bugs.launchpad.net/bugs/1858877 Title: Silent wasted storage with multiple RBD backends Status in OpenStack Compute (nova): New Bug description: Nova does not currently support multiple rbd backends. However, Glance does and an operator may point Nova at a Glance with access to multiple RBD clusters. If this happens, Nova will silently download the image from Glance, flatten it, and upload it to the local RBD cluster named privately to the image. If another instance is booted from the same image, this will happen again, using more network resources and duplicating the image on ceph for the second and subsequent instances. When configuring Nova and Glance for shared RBD, the expectation is that instances are fast-cloned from Glance base images, so this silent behavior of using a lot of storage would be highly undesirable and unexpected. Since operators control the backend config, but users upload images (and currently only to one backend), it is the users that would trigger this additional consumption of storage. This isn't really a bug in Nova per se, since Nova does not claim to support multiple backends and is download/uploading the image in the same way it would if the image was located on any other not-the-same- as-my-RBD-cluster location. It is, however, unexpected and undesirable behavior. To manage notifications about this bug go to: https://bugs.launchpad.net/nova/+bug/1858877/+subscriptions -- Mailing list: https://launchpad.net/~yahoo-eng-team Post to : yahoo-eng-team@lists.launchpad.net Unsubscribe : https://launchpad.net/~yahoo-eng-team More help : https://help.launchpad.net/ListHelp