From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:52208) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SznnO-0003mf-6j for qemu-devel@nongnu.org; Fri, 10 Aug 2012 07:54:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SznnL-0002pl-GB for qemu-devel@nongnu.org; Fri, 10 Aug 2012 07:54:26 -0400 Received: from mail.profihost.ag ([85.158.179.208]:43166) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SznnL-0002pZ-5G for qemu-devel@nongnu.org; Fri, 10 Aug 2012 07:54:23 -0400 Message-ID: <5024F66D.8050905@profihost.ag> Date: Fri, 10 Aug 2012 13:54:21 +0200 From: Stefan Priebe - Profihost AG MIME-Version: 1.0 References: <502283FA.2080506@profihost.ag> <5022912B.2000607@redhat.com> <50235527.4090804@profihost.ag> <50236059.7060801@redhat.com> <4A799203-5BFF-4DE9-9B85-459096EBEC22@profihost.ag> <50236484.2090702@redhat.com> <502369C7.7000300@profihost.ag> <50238E2A.1050203@profihost.ag> <5024D2E7.40700@profihost.ag> <5024E06A.4070603@redhat.com> <5024E232.5020706@profihost.ag> <5024E2CB.2050208@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] virtio-scsi vs. virtio-blk List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: ronnie sahlberg Cc: Paolo Bonzini , qemu-devel , Stefan Hajnoczi http://www.nexenta.com/corp/products/what-is-openstorage/nexentastor tells me: "SCSI UNMAP as a client-side feature frees up storage in the back end, in the context of thin provisioning (a 100-to-one reduction in space for VDI when using NexentaStor)." So i would say nexenta supports it. But i'm using virtio-scsi-pci? I'm really sorry to ask so many questions. Stefan Am 10.08.2012 13:20, schrieb ronnie sahlberg: > On Fri, Aug 10, 2012 at 8:30 PM, Paolo Bonzini wrote: >> Il 10/08/2012 12:28, Stefan Priebe - Profihost AG ha scritto: >>> I'm using iscsi. So no raw or qcow2. >> >> Ok, then you need to use scsi-block as your device instead of scsi-disk >> or scsi-hd. This will disable the QEMU SCSI emulation and let your VM >> talk directly to the NAS. >> >> CCing Ronnie who may be interested in bug reports since I'm on holiday >> starting "soon". >> > > I think it works on any, > You can of course not boot from a if=scsi disk in qemu, > > but any '-drive file=iscsi://...,if=scsi' should work as long as it is > not the boot device. > > SCSI emulation in qemu picks this up via WRITESAME10/16 and then calls > bdrv_aio_discard() > block/iscsi.c is invoked for discard and then translates this back to > a SBC UNMAP command it sends to the target. > > > Now, block/iscsi.c does assume that any target that reports that it > supports thin-provisioning actually implements UNMAP command. > There could be targets that support thin-provision ing that does NOT > support UNMAP and unly support discard via WRITESAME10/16 > so at some stage I should send a patch to iscsi.c to check which > commands the target supprots and use one of the supported ones instead > of a blanket > "you say you support thin-provisioning, I take that as confirmation > you support SBC UNMAP" > > > regards > ronnie sahlberg >