From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A500C4363A for ; Tue, 20 Oct 2020 14:24:13 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 72C2722244 for ; Tue, 20 Oct 2020 14:24:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 72C2722244 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35824 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kUsYd-00083d-6N for qemu-devel@archiver.kernel.org; Tue, 20 Oct 2020 10:24:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40748) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kUsXR-0007Ai-P9; Tue, 20 Oct 2020 10:22:57 -0400 Received: from mga09.intel.com ([134.134.136.24]:28766) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kUsXO-0007iJ-Aj; Tue, 20 Oct 2020 10:22:57 -0400 IronPort-SDR: MVyTYVvJkt55xHocMz2O/sywcwWt/Rb2TetNptpzSO3R6UZyftsRY5sVoOhO1Tbh+aoT+IFPqA mdKJRMJzdrAQ== X-IronPort-AV: E=McAfee;i="6000,8403,9779"; a="167333558" X-IronPort-AV: E=Sophos;i="5.77,397,1596524400"; d="scan'208";a="167333558" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Oct 2020 07:22:46 -0700 IronPort-SDR: KzAQepGVWaI+/qBP7cTvU7u9nLm+6DFHsHHZ9ZdCayxgRWwo2LU0lmcv3RRlTg7uzptn8jSQJJ re3igYZB6cCA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,397,1596524400"; d="scan'208";a="422517259" Received: from fmsmsx603.amr.corp.intel.com ([10.18.126.83]) by fmsmga001.fm.intel.com with ESMTP; 20 Oct 2020 07:22:46 -0700 Received: from shsmsx603.ccr.corp.intel.com (10.109.6.143) by fmsmsx603.amr.corp.intel.com (10.18.126.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Tue, 20 Oct 2020 07:22:45 -0700 Received: from shsmsx601.ccr.corp.intel.com (10.109.6.141) by SHSMSX603.ccr.corp.intel.com (10.109.6.143) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Tue, 20 Oct 2020 22:22:44 +0800 Received: from shsmsx601.ccr.corp.intel.com ([10.109.6.141]) by SHSMSX601.ccr.corp.intel.com ([10.109.6.141]) with mapi id 15.01.1713.004; Tue, 20 Oct 2020 22:22:44 +0800 From: "Wang, Wei W" To: Kevin Wolf Subject: RE: Question on Compression for Raw Image Thread-Topic: Question on Compression for Raw Image Thread-Index: Adamfp2lUlxQj0EMRyaTLkAdXyA8Qf//6umA//8QuPA= Date: Tue, 20 Oct 2020 14:22:43 +0000 Message-ID: <6124d55766e4477299a5796a002276a0@intel.com> References: <516589845d6f42d0b00784d16b59b5dc@intel.com> <20201020080051.GA4452@merkur.fritz.box> In-Reply-To: <20201020080051.GA4452@merkur.fritz.box> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: dlp-product: dlpe-windows dlp-reaction: no-action dlp-version: 11.5.1.3 x-originating-ip: [10.239.127.36] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Received-SPF: pass client-ip=134.134.136.24; envelope-from=wei.w.wang@intel.com; helo=mga09.intel.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/20 10:22:47 X-ACL-Warn: Detected OS = FreeBSD 9.x or newer [fuzzy] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "lersek@redhat.com" , "qemu-devel@nongnu.org" , "qemu-block@nongnu.org" , "mreitz@redhat.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tuesday, October 20, 2020 4:01 PM, Kevin Wolf wrote: > Am 20.10.2020 um 03:31 hat Wang, Wei W geschrieben: > > Hi, > > > > Does anyone know the reason why raw-format.c doesn't have > compression > > support (but qcow has the supported added)? For example, raw image > > backup with compression, "qemu-img convert -c -O raw origin.img > > dist.img", doesn't work. >=20 > A raw image is by definition a file that contains the exact same sequence= of > bytes as the guest sees, without any additional information or encoding. = If > you compress a raw file, the guest will see compressed data on its hard d= isk > instead of the real data. Ok, thanks. I'm thinking QEMU could do decompression of the compressed data= in raw.img when guest reads data. >=20 > Anything you could do to add transparent compression to it would mean tha= t > it's not a raw image any more, but a new image format. >=20 Yes, decompression makes it transparent to the guest. Would you think it's = good to reuse the raw image implementation, just add the compress/decompres= s option? Thanks, Wei