Red Hat Ceph Storage: aborted: Failure prepping block device

Solution Unverified - Updated -


  • Red Hat Ceph Storage
  • Red Hat Openstack 6
  • Red Hat Openstack 7


We are trying to build an instance using a 100GB rhel6.6 raw image and get the following error.

Build of instance 516f17c4-580d-4d9b-8588-1fc63bd6962b aborted: Failure prepping block device.
File "/usr/lib/python2.7/site-packages/nova/compute/", line 2075, in do_build_and_run_instance filter_properties) File "/usr/lib/python2.7/site-packages/nova/compute/", line 2174, in _build_and_run_instance 'create.error', fault=e) File "/usr/lib/python2.7/site-packages/nova/openstack/common/", line 82, in exit six.reraise(self.type, self.value, self.tb) File "/usr/lib/python2.7/site-packages/nova/compute/", line 2147, in _build_and_run_instance block_device_mapping) as resources: File "/usr/lib64/python2.7/", line 17, in enter return File "/usr/lib/python2.7/site-packages/nova/compute/", line 2285, in _build_resources reason=msg)


  • Modify /etc/glance/glance-api.conf to include the following.
  • Restart the glance-api service and nova-compute.
service openstack-glance-api restart
service nova-compute restart 

Red Hat Openstack 7 Director
For an automated way to set the show_image_direct_url parameter when a ceph backend is being used with OSP-d, bugzilla Enable glance-api show_image_direct_url for COW has been filed to track the backport of upstream fix .

As a workaround the following modification needs to be done to the OSP-d template to achieve the same. Add the glance::api::show_image_direct_url line to the controller.yaml hieradata file:

$ diff -u /usr/share/openstack-tripleo-heat-templates/puppet/hieradata/controller.yaml my_templates/puppet/hieradata/controller.yaml 

--- /usr/share/openstack-tripleo-heat-templates/puppet/hieradata/controller.yaml        2015-10-01 10:30:10.000000000 -0400
+++ my_templates/puppet/hieradata/controller.yaml       2015-11-23 14:57:02.466280952 -0500
@@ -62,6 +62,7 @@

 # glance
 glance::api::pipeline: 'keystone'
+glance::api::show_image_direct_url: true
 glance::registry::pipeline: 'keystone'
 glance::backend::swift::swift_store_create_container_on_put: true
 glance_file_pcmk_directory: '/var/lib/glance/images'

Root Cause

  • The operation times out because the full image is being pushed from Glance to Cinder instead of using copy on write snapshots.

Diagnostic Steps

  • Find an instance of the error in the nova-compute.log
2015-10-06 12:07:44.155 15544 ERROR nova.compute.manager [-] [instance: 139da521-38a9-4cd8-a55e-b8c67518d53b] Build of instance 139da521-38a9-4cd8-a55e-b8c67518d53b aborted: Failure prepping block device.
  • If we dump out the entire transaction by grepping for the instance ID we can see there is an earlier timeout error.
2015-10-06 12:07:44.132 15544 TRACE nova.compute.manager [instance: 139da521-38a9-4cd8-a55e-b8c67518d53b] VolumeNotCreated: Volume 9a8a9c83-a757-43cd-bba5-3d94a3336b49 did not finish being created even after we waited 188 seconds or 61 attempts.

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