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Re: [Xen-devel] Re: [PATCH] Fix restore handling checks

To: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH] Fix restore handling checks
From: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 23 Jun 2010 13:33:34 +0100
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>, Michal Novotny <minovotn@xxxxxxxxxx>, "'xen-devel@xxxxxxxxxxxxxxxxxxx'" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
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On Wed, 23 Jun 2010 13:04:26 +0100
Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:

> Michal Novotny writes ("Re: [PATCH] Fix restore handling checks"):
> > Are you saying that it's OK for administrators to violate the IDE specs 
> > and do it the way that is should never be done since this way it's not 
> > working on bare-metal systems ? This is the breach and it shouldn't be 
> > done this way so why to allow it? Shouldn't we care the code complies 
> > with the specifications to have it done the right way?
> 
> The job of the programmer is to give effect to the wishes of the
> users, not to comply with rules from elsewhere.  If the wishes of the
> users conflict with rules from elsewhere, including specs, then the
> programmer should do what the user wants.

So why doesn't Xen automatically produce free ice cream when the server
room gets warm ? and why doesn't Xen support storing 1Tb of data on a
40GB disc ? These are what the user wants.

That said there is nothing forbidding read only IDE media. It's unusual
and in the real world you normally only encounter it via hardware plugins
used for forensics work (so you can mirror a device and stand up in court
and say 'Neither I nor my system could have modified the contents of the
disc').

I guess the elegant way would be to present a read only IDE volume as a
magneto optical (ie ATAPI disc) but simply aborting (0x04) any write
commands isn't any different to what some of the drive protection widgets
do.

Alan

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