From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=54499 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OHGsZ-0006Kn-UY for qemu-devel@nongnu.org; Wed, 26 May 2010 09:42:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OHGsS-0007Gi-Lo for qemu-devel@nongnu.org; Wed, 26 May 2010 09:42:39 -0400 Received: from mail-pw0-f45.google.com ([209.85.160.45]:45531) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OHGsS-0007GM-Gf for qemu-devel@nongnu.org; Wed, 26 May 2010 09:42:32 -0400 Received: by pwj7 with SMTP id 7so1487836pwj.4 for ; Wed, 26 May 2010 06:42:31 -0700 (PDT) Message-ID: <4BFD2542.9090003@codemonkey.ws> Date: Wed, 26 May 2010 08:42:26 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [PATCH] Add cache=volatile parameter to -drive References: <1274091292-4812-1-git-send-email-agraf@suse.de> <4BF14CE9.5040907@suse.de> <4BF15DC8.8080104@codemonkey.ws> <201005171723.15675.paul@codesourcery.com> <4BF16E22.6090400@codemonkey.ws> <4BFC0FF6.1080005@suse.de> <20100525210113.GE1402@hall.aurel32.net> <4BFC79E8.1070700@codemonkey.ws> <4BFCDF4D.5020703@redhat.com> In-Reply-To: <4BFCDF4D.5020703@redhat.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org, Paul Brook , Alexander Graf , Aurelien Jarno , hch@lst.de On 05/26/2010 03:43 AM, Kevin Wolf wrote: > Am 26.05.2010 03:31, schrieb Anthony Liguori: > >> On 05/25/2010 04:01 PM, Aurelien Jarno wrote: >> >>> I really think this patch can be useful, in my own case when testing >>> debian-installer (I already cache=writeback). In short all that is about >>> developing and testing, as opposed to run a VM in production, can >>> benefit about that. This was one of the original use case of QEMU before >>> KVM arrived. >>> >>> Unless someone can convince me not to do it, I seriously considering >>> applying this patch. >>> >>> >> There really needs to be an indication in the --help output of what the >> ramifications of this option are, in the very least. It should also be >> removable via a ./configure option because no sane distribution should >> enable this for end users. >> > We know better what you stupid user want? What percentage of qemu users do you think have actually read qemu-doc.texi? It's not a stretch for someone to have heard that cache options can improve performance, and then see cache=volatile in the help output, try it, and then start using it because they observe a performance improvement. That's not being stupid. I think it's a reasonable expectation for a user to have that their data is safe. Regards, Anthony Liguori > There are valid use cases for > this cache option, most notably installation. > > I could agree with requesting that the option should be called > cache=unsafe (or even Alex' cache=destroys_your_image), but that should > really be enough to tell everyone that his data is not safe with this > option. > > Kevin >