On Fri, Jan 13, 2017 at 5:11 AM, Vincent Godin <vince.ml...@gmail.com> wrote:
> We are using a production cluster which started in Firefly, then moved to
> Giant, Hammer and finally Jewel. So our images have different features
> correspondind to the value of "rbd_default_features" of the version when
> they were created.
> We have actually three pack of features activated :
> image with :
> - layering ~ 1
> - layering, striping ~3
> - layering, exclusive-lock, object-map, fast-diff, deep-flatten ~ 61
> 1) Is it a good idea to try to give all images the same features ?

It isn't needed.

> 2) Is it possible to disable the striping feature on an already created
> image (we never specify any stripe-unit nor stripe-count) ?

Negative -- striping cannot be dynamically disabled because it would
result in potentially altering the structure and placement of the data
within the image. If your stripe-unit is the object size and the
stripe count is 1, that's a special case where the flag is essentially

> 3) What is the behaviour of an already created image on which we activate
> the object-map feature ? Will a process try to rebuild a index of used
> blocks - if no, if we delete later the image, will ceph try to remove all
> the blocks or only the blocks refered by object-map index ?

You would need to run "rbd object-map rebuild <image-spec>" to rebuild
the object map. Until it is rebuilt, it will be considered invalid and
won't be used for reference. You can determine the object map state by
running "rbd info <image-spec>"

> 4) We are on Jewel but with tunables set to hammer (Centos 7.2). What are
> the best default features to set in that case ? (we use Ceph  under an
> Openstack for glance, nova and cinder

We feel like the current defaults are a good mix of features for
everyday use of non-shared images or non-krbd images. Most
importantly, all the default features can be dynamically disabled if
your needs for the image change.

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