Let me make the issue more clear. Suppose I cloned image A from a parent image and create snap1 for image A and then make some change of image A. If I did the rbd export-diff @snap1. how should I prepare the existing image B to make sure it will be exactly same with image A@snap1 after import-diff against this image B.
Thanks, Zhongyan On Wed, Nov 23, 2016 at 11:34 AM, Zhongyan Gu <zhongyan...@gmail.com> wrote: > Thanks Jason, very clear explanation. > However, I found some strange behavior when export-diff on a cloned image, > not sure it is a bug on calc_snap_set_diff(). > The test is, > Image A is cloned from a parent image. then create snap1 for image A. > The content of export-diff A@snap1 will be changed when update image A. > Only after image A has no overlap with parent, the content of export-diff > A@snap1 is stabled, which is almost zero. > I don't think it is a designed behavior. export-diff A@snap1 should > always get a stable output no matter image A is cloned or not. > > Please correct me if anything wrong. > > Thanks, > Zhongyan > > > > > On Tue, Nov 22, 2016 at 10:31 PM, Jason Dillaman <jdill...@redhat.com> > wrote: > >> On Tue, Nov 22, 2016 at 5:31 AM, Zhongyan Gu <zhongyan...@gmail.com> >> wrote: >> > So if initial snapshot is NOT specified, then: >> > rbd export-diff image@snap1 will diff all data to snap1. this cmd >> equals to >> > : >> > rbd export image@snap1. Is my understand right or not?? >> >> >> While they will both export all data associated w/ image@snap1, the >> "export" command will generate a raw, non-sparse dump of the full >> image whereas "export-diff" will export only sections of the image >> that contain data. The file generated from "export" can be used with >> the "import" command to create a new image, whereas the file generated >> from "export-diff" can only be used with "import-diff" against an >> existing image. >> >> -- >> Jason >> > >
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