openstack team mailing list archive

[Rick Harris <rick.harris@xxxxxxxxxxxxx>]

>What's the difference between an image and an object?  They're all just blobs of bits as far as I > thought.

I think of an image as data+metadata.

The data is stored as objects where the image can span multiple objects.

The metadata maybe stored in the form of a manifest-file, or, as with Glance, is stored as an entry in the registry.

As has been discussed on the ML, there is a need for a container format (OVF?), which can encapsulate both the data and metadata if we want to be able to shuffle around fully contained images.

As it stands with Glance, the data and metadata are separate; so, in order to replicate an image, you need to pull the image's objects and, in a separate step, fetch its metadata.

________________________________________
From: openstack-bounces+rick.harris=rackspace.com@xxxxxxxxxxxxxxxxxxx [openstack-bounces+rick.harris=rackspace.com@xxxxxxxxxxxxxxxxxxx] on behalf of Ewan Mellor [Ewan.Mellor@xxxxxxxxxxxxx]
Sent: Monday, January 17, 2011 12:12 PM
To: 'Jay Pipes'
Cc: openstack@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Openstack] Deprecating nova-objectstore

> -----Original Message-----
> From: Jay Pipes [mailto:jaypipes@xxxxxxxxx]
> Sent: 17 January 2011 18:08
> To: Ewan Mellor
> Cc: Thierry Carrez; openstack@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Openstack] Deprecating nova-objectstore
>
> On Mon, Jan 17, 2011 at 12:38 PM, Ewan Mellor
> <Ewan.Mellor@xxxxxxxxxxxxx> wrote:
> >> -----Original Message-----
> >> From: Jay Pipes [mailto:jaypipes@xxxxxxxxx]
> >> Sent: 17 January 2011 17:17
> >> To: Ewan Mellor
> >> Cc: Thierry Carrez; openstack@xxxxxxxxxxxxxxxxxxx
> >> Subject: Re: [Openstack] Deprecating nova-objectstore
> >>
> >> On Mon, Jan 17, 2011 at 10:53 AM, Ewan Mellor
> >> <Ewan.Mellor@xxxxxxxxxxxxx> wrote:
> >> > We could do it in two steps.  You could set up nova-compute ->
> Glance
> >> -> nova-objectstore (testing purposes only).  This would allow us to
> >> remove the S3 code from Nova, but people could still use nova-
> >> objectstore if they don't want to set up Swift.
> >>
> >> This is already done in Bexar, as Chris MacGown completed the S3
> >> backend for Glance. What is NOT the same, though, is that people
> would
> >> not be speaking the s3 API as they do now... they would speak the
> >> Glance REST-like API instead...
> >
> > Yes, that's what I meant -- make Glance the only thing that speaks
> S3, and then we can remove the S3 code from Nova in favour of Glance.
> >
> >> Plus, objects are a superset of
> >> images; Glance only stores images, not all objects...
> >
> > What does this mean?  I didn't even know that anyone was
> distinguishing between an image and an object.
>
> All images are objects but not all objects are images.  Swift/S3 can
> be used to store anything, not just images, that's what I meant. :)

What's the difference between an image and an object?  They're all just blobs of bits as far as I thought.

Ewan.
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