I can only speak for some environments, but sometimes, you would want to make sure that a cluster cannot fill up until you can add more capacity.
Some organizations are unable to purchase new capacity rapidly and making sure you cannot exceed your current capacity, then you can't run into problems.
It may also come from an understanding that thick provisioning will provide more performance initially like virtual machines environment.
Having said all of this, isn't there a way to make sure the cluster can accommodate the size of all RBD images that are created. And ensure they have the space available? Some service availability might depend on making sure the storage can provide the necessary capacity.
I'm assuming that this is all from an understanding that it is more costly to run such type of environments, however, you can also guarantee that you will never fill up unexpectedly your cluster.
Sam
On Oct 18, 2017 02:20, "Wido den Hollander" <wido@xxxxxxxx> wrote:
> Op 17 oktober 2017 om 19:38 schreef Jason Dillaman <jdillama@xxxxxxxxxx>:
>Indeed. It makes me wonder why anybody would want it. It will:
>
> There is no existing option to thick provision images within RBD. When
> an image is created or cloned, the only actions that occur are some
> small metadata updates to describe the image. This allows image
> creation to be a quick, constant time operation regardless of the
> image size. To thick provision the entire image would require writing
> data to the entire image and ensuring discard support is disabled to
> prevent the OS from releasing space back (and thus re-sparsifying the
> image).
>
- Impact recovery performance
- Impact scrubbing performance
- Utilize more space then needed
Why would you want to do this Sinan?
Wido
> On Mon, Oct 16, 2017 at 10:49 AM, <sinan@xxxxxxxx> wrote:
> > Hi,
> >
> > I have deployed a Ceph cluster (Jewel). By default all block devices that
> > are created are thin provisioned.
> >
> > Is it possible to change this setting? I would like to have that all
> > created block devices are thick provisioned.
> >
> > In front of the Ceph cluster, I am running Openstack.
> >
> > Thanks!
> >
> > Sinan
> >
> > _______________________________________________
> > ceph-users mailing list
> > ceph-users@xxxxxxxxxxxxxx
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>
>
>
> --
> Jason
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