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 <[email protected]> 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 <[email protected]> > 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 <[email protected]> >> wrote: >> >>> and better explained here: >>> http://ceph.com/docs/master/rbd/qemu-rbd/ >>> >>> On Thu, May 28, 2015 at 6:02 AM, David Medberry <[email protected]> >>> 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 <[email protected]> >>>> 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 >>>>> [email protected] >>>>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators >>>>> >>>>> >>>> >>> >>> _______________________________________________ >>> OpenStack-operators mailing list >>> [email protected] >>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators >>> >>> >> > > _______________________________________________ > OpenStack-operators mailing list > [email protected] > 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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