From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Brook Subject: Re: [Qemu-devel] Re: [PATCH] virtio-blk: add SGI_IO passthru support Date: Wed, 29 Apr 2009 12:29:58 +0100 Message-ID: <200904291229.59766.paul@codesourcery.com> References: <20090427082606.GA32604@lst.de> <200904291211.20374.paul@codesourcery.com> <200904291319.05247.borntraeger@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, Christoph Hellwig , Anthony Liguori , kvm@vger.kernel.org, Rusty Russell , Hannes Reinecke To: Christian Borntraeger Return-path: Received: from mail.codesourcery.com ([65.74.133.4]:51480 "EHLO mail.codesourcery.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750965AbZD2LaD (ORCPT ); Wed, 29 Apr 2009 07:30:03 -0400 In-Reply-To: <200904291319.05247.borntraeger@de.ibm.com> Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: On Wednesday 29 April 2009, Christian Borntraeger wrote: > Am Wednesday 29 April 2009 13:11:19 schrieb Paul Brook: > > On Wednesday 29 April 2009, Christoph Hellwig wrote: > > > On Tue, Apr 28, 2009 at 11:37:01AM -0500, Anthony Liguori wrote: > > > > Ah, excellent. I think that's a great thing to do. So do you think > > > > virtio-scsi would deprecate virtio-blk? > > > > > > I don't think so. If you have an image format or a non-scsi > > > blockdevice underneath virtio-block avoids the encoding into SCSI CDBs > > > and back and should be faster. > > > > Is this actually measurably faster, or just infinitesimally faster in > > theory? > > If the underlying backing is 4k block size and the emulated scsi disk has > 512 byte block size, write performance can be a lot slower. Rubbish. If this is really a problem you can just use a scsi disk with 4k sectors. Paul