Re: [Qemu-devel] Re: Strategic decision: COW format

[Avi Kivity <avi@redhat.com>]

On 02/23/2011 05:33 PM, Daniel P. Berrange wrote:
> On Wed, Feb 23, 2011 at 05:23:33PM +0200, Avi Kivity wrote:
> >  On 02/23/2011 04:23 PM, Anthony Liguori wrote:
> >  >On 02/23/2011 07:43 AM, Avi Kivity wrote:
> >  >>On 02/22/2011 10:56 AM, Kevin Wolf wrote:
> >  >>>*sigh*
> >  >>>
> >  >>>It starts to get annoying, but if you really insist, I can repeat it
> >  >>>once more: These features that you don't need (this is the correct
> >  >>>description for what you call "misfeatures") _are_ implemented in a way
> >  >>>that they don't impact the "normal" case. And they are it today.
> >  >>>
> >  >>
> >  >>Plus, encryption and snapshots can be implemented in a way that
> >  >>doesn't impact performance more than is reasonable.
> >  >
> >  >We're still missing the existence proof of this, but even assuming
> >  >it existed,
> >
> >  dm-crypt isn't any more complicated, and it's used by default in
> >  most distributions these days.
>
> IMHO dm-crypt isn't a generally usable alternative to native built
> in encryption in qcow2. It isn't usable at all by non-root. If you
> want to use with plain files, then you need to turn the file into
> a loopback device and then layer in dm-crypt. It is generally
> just a PITA to manage.

I wasn't suggesting dm-crypt is a replacement for qcow2 encyption, just 
that it shows that block-level encryption can be done with reasonable 
overhead.

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