Open Stack

yep. It's at the CEPH level (not the XFS level.)

On Thu, May 28, 2015 at 8:40 AM, Stephen Cousins <steve.cousins at maine.edu>
wrote:

> Hi David,
>
> So Ceph will use Copy-on-write even with XFS?
>
> Thanks,
>
> Steve
>
> On Thu, May 28, 2015 at 10:36 AM, David Medberry <openstack at medberry.net>
> wrote:
>
>> This isn't remotely related to btrfs. It works fine with XFS. Not sure
>> how that works in Fuel, never used it.
>>
>> On Thu, May 28, 2015 at 8:01 AM, Forrest Flagg <fostro.flagg at gmail.com>
>> wrote:
>>
>>> I'm also curious about this.  Here are some other pieces of information
>>> relevant to the discussion.  Maybe someone here can clear this up for me as
>>> well.  The documentation for Fuel 6.0, not sure what they changed for 6.1,
>>> [1] states that when using Ceph one should disable qcow2 so that images are
>>> stored in raw format.  This is due to the fact that Ceph includes its own
>>> mechanisms for copy-on-write and snapshots.  According to the Ceph
>>> documentation [2], this is true only when using a BTRFS file system, but in
>>> Fuel 6.0 Ceph uses XFS which doesn't provide this functionality.  Also, [2]
>>> recommends not using BTRFS for production as it isn't considered fully
>>> mature.  In addition, Fuel 6.0 [3] states that OpenStack with raw images
>>> doesn't support snapshotting.
>>>
>>> Given this, why does Fuel suggest not using qcow2 with Ceph?  How can
>>> Ceph be useful if snapshotting isn't an option with raw images and qcow2
>>> isn't recommended?  Are there other factors to take into consideration that
>>> I'm missing?
>>>
>>> [1]
>>> https://docs.mirantis.com/openstack/fuel/fuel-6.0/terminology.html#qcow2
>>> [2]
>>> http://ceph.com/docs/master/rados/configuration/filesystem-recommendations/
>>> [3]
>>> https://docs.mirantis.com/openstack/fuel/fuel-6.0/user-guide.html#qcow-format-ug
>>>
>>> Thanks,
>>>
>>> Forrest
>>>
>>> On Thu, May 28, 2015 at 8:02 AM, David Medberry <openstack at medberry.net>
>>> wrote:
>>>
>>>> and better explained here:
>>>> http://ceph.com/docs/master/rbd/qemu-rbd/
>>>>
>>>> On Thu, May 28, 2015 at 6:02 AM, David Medberry <openstack at medberry.net
>>>> > wrote:
>>>>
>>>>> The primary difference is the ability for CEPH to make zero byte
>>>>> copies. When you use qcow2, ceph must actually create a complete copy
>>>>> instead of a zero byte copy as it cannot do its own copy-on-write tricks
>>>>> with a qcow2 image.
>>>>>
>>>>> So, yes, it will work fine with qcow2 images but it won't be as
>>>>> performant as it is with RAW. Also, it will actually use more of the native
>>>>> underlying storage.
>>>>>
>>>>> This is also shown as an Important Note in the CEPH docs:
>>>>> http://ceph.com/docs/master/rbd/rbd-openstack/
>>>>>
>>>>> On Thu, May 28, 2015 at 4:12 AM, Shake Chen <shake.chen at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hi
>>>>>>
>>>>>> Now I try to use Fuel 6.1 deploy openstack Juno, use Ceph as cinder,
>>>>>> nova and glance backend.
>>>>>>
>>>>>> In Fuel document suggest if use ceph, suggest use RAW format image.
>>>>>>
>>>>>> but if I upload qcow2 image, seem working well.
>>>>>>
>>>>>> what is the different use qcow2 and RAW in Ceph?
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Shake Chen
>>>>>>
>>>>>>
>>>>>> _______________________________________________
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>>>>>> OpenStack-operators at lists.openstack.org
>>>>>>
>>>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators
>>>>>>
>>>>>>
>>>>>
>>>>
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>>>
>>
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>>
>
>
> --
> ________________________________________________________________
>  Steve Cousins             Supercomputer Engineer/Administrator
>  Advanced Computing Group            University of Maine System
>  244 Neville Hall (UMS Data Center)              (207) 561-3574
>  Orono ME 04469                      steve.cousins at maine.edu
>
>
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