Hum ok I tested on some VM images, and haven't seen any noticeable differences in term of output size (this is indeed faster) Thanks for the information ! On 03/09/2018 05:10 PM, Jason Dillaman wrote: > On Fri, Mar 9, 2018 at 11:05 AM, <ceph@xxxxxxxxxxxxxx> wrote: >> Hi, >> >> I am looking for information regarding rbd's --whole-object option >> According to the doc: >> --whole-object >> Specifies that the diff should be limited to the extents of a full >> object instead of showing intra-object deltas. When the object map >> feature is enabled on an image, limiting the diff to the object extents >> will dramatically improve performance since the differences can be >> computed by examining the in-memory object map instead of querying RADOS >> for each object within the image. >> >> Is there any drawback ? > > The only drawback is that your export-diff might be larger. For > example, changing 1 bytes within a 4MB backing object block will > result in a 4MB export instead of a 1 byte export. > >> If I use this option when object-map is enabled, is this only benefical ? >> What does it do if this feature is disabled ? > > It behaves the same way -- it will export the full object if at least > one byte has changed. > >> Why is `whole-object` an option, and not the default behavior ? > > ... because it can result in larger export-diffs. > >> Regards, >> _______________________________________________ >> ceph-users mailing list >> ceph-users@xxxxxxxxxxxxxx >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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