During a conversion process cinder can overfill a controller root file system

[Ivan Kolodyazhny]

When I create a new volume from a very large QCOW image (virtual size) the root file system of a controller might be overfilled because the cinder downloads the full size image to the /var/lib/cinder/conversion/ directory

Steps to reproduce:
Install one controller and two ceph/compute nodes. The controller has to have the minimal possible size of a root filesystem (20GB). Ceph size should be enough to keep about 30GB. Create a QCOW2 image with large virtual size and upload it to Glance:

root@node-2:/var/lib/nova/tmp# qemu-img info ubuntu_qcow_20GB.qcow2
image: ubuntu_qcow_20GB.qcow2
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 835M
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

Then try to create a new volume from this image:
root@node-1:~# cinder create --image-id 4a5c016b-dff0-4e52-b640-bd63528911a6 --name volume_from_image_20GB 20

During the conversion Cinder will download the whole image to the /var/lib/cinder/conversion/ directory and it might overfill the root directory of a controller node

Expected results:
Root filesystem should not be overfilled

Workaround:
1. To keep images in Raw format in Ceph so that Cinder does not download them but perform snapshots in Ceph storage
2. To forcefully separate /var from the root file system

This bug also affect other cinder backends

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/415868

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/415868
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=494264e797107a36804f8d25d0e6af246e0a140b
Submitter: Jenkins
Branch: master

commit 494264e797107a36804f8d25d0e6af246e0a140b
Author: Ivan Kolodyazhny <email address hidden>
Date: Fri Dec 30 13:46:26 2016 +0200

    Check if volume node has enough space for image operations

    Add check if free space is more than image size before downloading and
    convertion.

    Change-Id: I66f9e50cc8b7135d58822e13f62dea91ccb37c23
    Closes-Bug: #1653225

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 10.0.0.0rc1 release candidate.

[Alexander Bozhenko (alexbozhenko)]

related: https://bugs.launchpad.net/cinder/+bug/1683228