yep. It's at the CEPH level (not the XFS level.) On Thu, May 28, 2015 at 8:40 AM, Stephen Cousins <steve.cous...@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 <openst...@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.fl...@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 <openst...@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 <openst...@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.c...@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 >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> OpenStack-operators mailing list >>>>>> OpenStack-operators@lists.openstack.org >>>>>> >>>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators >>>>>> >>>>>> >>>>> >>>> >>>> _______________________________________________ >>>> OpenStack-operators mailing list >>>> OpenStack-operators@lists.openstack.org >>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators >>>> >>>> >>> >> >> _______________________________________________ >> OpenStack-operators mailing list >> OpenStack-operators@lists.openstack.org >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators >> >> > > > -- > ________________________________________________________________ > 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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