Ceph's RBD Format 2 images support the copy-on-write clones/snapshots for quick
provisioning, where essentially the following happens:
Snapshot of Image created --> Snapshot protected from deletion --> Clone image
created from snapshot
The protected snapshot acts as a base image for the clone, where only the
additional data is stored in the clone. See more here:
http://ceph.com/docs/master/rbd/rbd-snapshot/#layering
For our environment here I have modified the included datastore/tm drivers for
Ceph to take advantage of these format 2 images/layering for Non-Persistent
images. It works rather well, and all image functions work appropriately for
non-persistent images (save as, etc.). One note/requirement is to be using a
newer Ceph release (recommend Dumpling or newer) and newer versions of
QEMU/Libvirt (there were some bugs in older releases, but the versions from
Ubuntu Cloud Archive for 12.04 work fine). I did submit them for improvement
prior to the 4.0 release, but the simple format 1 images are the default
currently for OpenNebula.
I think this would be a good question for the developers. Would creating the
option for Format 2 images (either in the image template as a parameter or on
the Datastore as a configuration attribute) and then developing the DS/TM
drivers further to accommodate this option be worth the effort? I can see use
cases for both (separate images vs. cloned images having to rely on the base
image), but cloned images are WAY faster to deploy.
I have the basic code for format 2 images, I think the logic for looking up the
parameter/attribute and then applying appropriate action should be rather
simple. Could collaborate/share if you'd like.
----- Original Message -----
From: "Kenneth" <kenn...@apolloglobal.net>
To: users@lists.opennebula.org
Sent: Thursday, December 12, 2013 6:11:15 AM
Subject: Re: [one-users] Ceph and thin provision
Yes, that is possible. But as I said, all my images were all preallocated as I
haven't created any image from sunstone.
---
Thanks,
Kenneth
Apollo Global Corp.
On 12/12/2013 06:25 PM, Michael wrote:
This doesn't appear to be the case, I've 2TB of images on Ceph and 380GB
data reported by Ceph (760G after replication). All of these Ceph images
were created through the Opennebula Sunstone template GUI.
-Michael
On 12/12/2013 09:11, Kenneth wrote:
<blockquote>
I haven't tried creating a thin or thick provision in ceph rbd from scratch. So
basically, I can say that a 100GB disk will consume 100GB RBD in ceph (of
course it will be 200GB in ceph storage since ceph duplicates the disks by
default).
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