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Date: Fri, 10 Sep 2010 14:46:49 -0300
Message-ID: <AANLkTikvT9GtVVqCTR=UEofUqJGiFEqTiKbrN6oktCDV@mail.gmail.com>
Subject: Re: [Qemu-devel] [RFC] qed: Add QEMU Enhanced Disk format
From: Miguel Di Ciurcio Filho <miguel.filho@gmail.com>
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>, Christoph Hellwig <hch@lst.de>

On Fri, Sep 10, 2010 at 2:10 PM, Anthony Liguori <anthony@codemonkey.ws> wrote:
>>
>> Well, snapshots have an ID today (which is different from their name).
>> Nobody stops you from putting a UUID there. Fully backwards compatible,
>> no feature flag needed. I think Miguel was planning to actually do this.
>>
>
> The problem is that management tools have to make a decision about what to
> do with ID's that aren't UUIDs which means that in our management interface,
> we can't just expose UUIDs but instead we have to expose strings that may
> sometimes be UUIDs.
>
> I don't think it buys us a lot to get the backwards compatibility.
>

My main idea is to do not expose any ID/UUID information to the user,
at least by default. Snapshots must have a name to be presented to the
user, if he/she does not provide one we create it [1].

As you said, the ID field in qcow2 is just a string, so if we put an
UUID there, no harm is done. The problem was to store parent
information. qcow2 has an extra_data area that can store anything, so
I used that space. This feature is an old wish from libvirt guys.

I could not follow all the details discussed about qed so far, but
would something like this work?

Regards,

Miguel

[1] commit 7d631a116ad8fe07001e2cc4c559a06aac82745f