On Tue, Jun 25, 2019 at 10:37 PM Tony <yaoguot@xxxxxxxxx> wrote: > > Hi all, > > Recently, I have been studying the influence of object-map on RBD export . > My expectation is that object-map can improve the speed of export > > But, I did not find any effect of object-map in the experiment. Then, > I look in the code for the reason. > I found that the object-map was ignored when rbd opened the image in > read-only mode, > and Open image read-only when export. > > I'm wondering why we can't open an image in read-only mode using > object-map feature. It's because the HEAD revision of the image is still mutable and you don't have any assurances that it isn't being modified in the background. If you take a snapshot and export the snapshot, the object-map will be used since the snapshot content is immutable. > In this case, the object-map feature does not seem to improve the > performance of rbd export . > > Your prompt reply will be appreciated. > Thanks. > > Guotao Yao -- Jason
