On 03/19/2013 11:03 PM, Chen, Xiaoxi wrote:
I think Josh may be the right man for this question ☺
To be more precious, I would like to add more words about the status:
1. We have configured “show_image_direct_url= Ture” in Glance, and from the Cinder-volume’s log, we can make sure we have got a direct_url , for example.
image_id 6565d775-553b-41b6-9d5e-ddb825677706
image_location rbd://6565d775-553b-41b6-9d5e-ddb825677706
2. In the _is_cloneable function, it tries to “_parse_location” the direct_url (rbd://6565d775-553b-41b6-9d5e-ddb825677706) into 4 parts : fsid,pool,volume,snapshot . Since the direct_url passed from Glance doesn’t provide fsid ,pool and snapshot info, the parse is failed and _is_cloneable return false, which will finally drop the request to RBDDriver::copy_image_to_volume.
This is working as expected - cloning was introduced in format 2 rbd
volumes, available in bobtail but not argonaut. When the image is
uploaded to glance, it is created as format 2 and a snapshot of it is
taken and protected from deletion if the installed version of librbd
(via the python-ceph package) supports it.
The location reported will be just the image id for format 1 images.
For format 2 images, it has 4 parts, as you noted. You may need to
update python-ceph and librbd1 on the node running glance-api
and re-upload the image so it will be created as format 2, rather
than the current image which is format 1, and thus cannot be cloned.
3. In Cinder/volume/driver.py,RBDDriver::copy_image_to_volume, we have seem this note:
# TODO(jdurgin): replace with librbd this is a temporary hack, since rewriting this driver to use librbd would take too long
And in this function, the cinder RBD driver download the whole image from Glance into a temp file in local Filesystem, then use rbd import to import the temp file into a RBD volume.
That note is about needing to remove the volume before importing the
data, instead of just writing to it directly with librbd.
This is absolutely not what we want (zero copy and CoW), so we digging into the _is_cloneable function
Seems the straightforward way to solve 2 ) write a patch for glance that adding more infos in the direct_url, but I am not sure if it’s possible for ceph to clone a RBD from pool A to pool B?
Cloning from one pool to another is certainly supported. If you're
interested in more details about cloning, check out the command line
usage [1] and internal design [2].
Josh
[1]
https://github.com/ceph/ceph/blob/master/doc/rbd/rbd-snapshot.rst#layering
[2] https://github.com/ceph/ceph/blob/master/doc/dev/rbd-layering.rst
From: ceph-users-bounces@xxxxxxxxxxxxxx [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Li, Chen
Sent: 2013年3月20日 12:57
To: 'ceph-users@xxxxxxxxxxxxxx'
Subject: create volume from an image
I'm using Ceph RBD for both Cinder and Glance. Cinder and Glance are installed in two machines.
I have get information from many place that when cinder and glance both using Ceph RBD, then no real data transmit will happen because of copy on write.
But the truth is when i run the command:
cinder create --image-id 6565d775-553b-41b6-9d5e-ddb825677706 --display-name test 3
I can still get network data traffic between cinder and glance.
And I check the cinder code, the image_location is None (cinder/volume/manager.py), which makes cinder will failed running cloned = self.driver.clone_image(volume_ref, image_location).
Is this a OpenStack (cinder or glance )bug ?
Or I have miss and configuration?
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