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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 574FEC433DF for ; Tue, 20 Oct 2020 08:02:56 +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 6CA1722247 for ; Tue, 20 Oct 2020 08:02:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="hdWNScPq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CA1722247 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58956 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kUmbd-0002W0-TW for qemu-devel@archiver.kernel.org; Tue, 20 Oct 2020 04:02:53 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38592) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kUmZq-0001Ww-JK for qemu-devel@nongnu.org; Tue, 20 Oct 2020 04:01:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:51723) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kUmZo-0005ng-0t for qemu-devel@nongnu.org; Tue, 20 Oct 2020 04:01:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1603180856; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=UEH/HNhJ33HBPjTmuEaMoNqGicGC4qesPUh3oBxDBRA=; b=hdWNScPqnnT4a7CqytsSqc5Lwse6thfsl0mpmLiF1ZLJiaknnzOTIqmUo2f62uu+/yVVqV 6+mDM/VyC4tP1E7mT2g7i+bS7qUqzw67w0fdBHUQN5Mfq+Crjlnxy9fiNyABbtWa6MbaWE g4D6aAZnVTSUiRanJHTUnabmQNU1Lqw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-594-mJTuNawVPN6rlHnDysV0FQ-1; Tue, 20 Oct 2020 04:00:55 -0400 X-MC-Unique: mJTuNawVPN6rlHnDysV0FQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 463DA1009E2B; Tue, 20 Oct 2020 08:00:54 +0000 (UTC) Received: from merkur.fritz.box (ovpn-112-88.ams2.redhat.com [10.36.112.88]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2AF636EF50; Tue, 20 Oct 2020 08:00:52 +0000 (UTC) Date: Tue, 20 Oct 2020 10:00:51 +0200 From: Kevin Wolf To: "Wang, Wei W" Subject: Re: Question on Compression for Raw Image Message-ID: <20201020080051.GA4452@merkur.fritz.box> References: <516589845d6f42d0b00784d16b59b5dc@intel.com> MIME-Version: 1.0 In-Reply-To: <516589845d6f42d0b00784d16b59b5dc@intel.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/20 01:15:43 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=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" 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. 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 disk instead of the real data. Anything you could do to add transparent compression to it would mean that it's not a raw image any more, but a new image format. Kevin