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Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive

From: Paul Brook
Subject: Re: [Qemu-devel] Re: [PATCH 2/2] Add flush=off parameter to -drive
Date: Tue, 11 May 2010 14:50:52 +0100
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> > In a development environment the rules can be a bit different. For
> > example if you're testing an OS installer then you really don't want to
> > be passing magic mount options. If the host machine dies then you don't
> > care about the state of the guest because you're going to start from
> > scratch anyway.
> Then create a mount point on your host and mount the host file system
> under that mount with barrier=0.
> The problem with options added for developers is that those options are
> very often accidentally used for production.

I disagree.  We should not be removing or rejecting features just because they 
allow you to shoot yourself in the foot.  We probably shouldn't be enabling 
them by default, but that's a whole different question.

Mounting a filesystem with barrier=0 is not a good answer because it's a 
global setting.  While my qemu VM may be disposable, it's unlikely that the 
same is true of the rest of my machine.  By your argument linux shouldn't be 
allowing me to do that in the first place because a dumb sysadmin could use 
that option on the filesystem containing the mail store. In fact with the 
average user that's *likely* to happen because they'll only have a single 
partition on their machine.


N.B. in this context "developers" refers to users who happen to be using qemu 
as part of a toolset for development of $whatever, not development of qemu 
itself. c.f. "production" where qemu is part of the IT infrastructure used to 
directly provide an external service.

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