> Date: Wed, 16 Oct 2013 16:06:49 +1300
> From: Mark Kirkwood <mark.kirkwood@xxxxxxxxxxxxxxx>
> To: Wido den Hollander <wido@xxxxxxxx>, ceph-users@xxxxxxxxxxxxxx
> Subject: Re: Is there a way to query RBD usage
> Message-ID: <525E02C9.9050904@xxxxxxxxxxxxxxx>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> On 16/10/13 15:53, Wido den Hollander wrote:
> > On 10/16/2013 03:15 AM, Blair Bethwaite wrote:
> >> I.e., can we see what the actual allocated/touched size of an RBD is in
> >> relation to its provisioned size?
> >>
> >
> > No, not an easy way. The only way would be to probe which RADOS
> > objects exist, but that's a heavy operation you don't want to do with
> > large images or with a large number of RBD images.
> >
>
> So maybe a 'df' arg for rbd would be a nice addition to blueprints?
Yes, I think so. It does seem a little conflicting to promote Ceph as doing thin-provisioned volumes, but then not actually be able to interrogate their real usage against the provisioned size. As a cloud admin using Ceph as my block-storage layer I really want to be able to look at several metrics in relation to volumes and tenants:
total GB quota, GB provisioned (i.e., total size of volumes&snaps), GB allocated
When users come crying for more quota I need to whether they're making efficient use of what they've got.
This actually leads into more of a conversation around the quota model of dishing out storage. IMHO it would be much more preferable to do things in a more EBS oriented fashion, where we're able to see actual usage in the backend. Especially true with snapshots - users are typically dismayed that their snapshots count towards their quota for the full size of the originally provisioned volume (despite the fact the snapshot could usually be truncated/shrunk by a factor of two or more).
--
Cheers,
~Blairo
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