From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from vps01.wiesinger.com (vps01.wiesinger.com [46.36.37.179]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9C3C126AF5 for ; Wed, 22 Jan 2025 07:29:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=46.36.37.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737530955; cv=none; b=EdHbqSBnXW5xeI3KtlzEP3nELfWAdA4o6fu3fW9dKEl1sBqJ+DQ2Z3lHcSiTj69cYP+Uy9abEhhVgq9p1y3kQglk9fwpn/xgPtIyhD7miq6PB3ZFHCX0tdCZZO6HZjbAlA4ZYFeJWGzhHDStlkDajJvNC07994sKqs6eNxKABiA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737530955; c=relaxed/simple; bh=T4/sZ9cLMF6CsYhYVN60Hu7UdAfBd5IHXw8JzARLIx4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XqqoslcdIKxTcJVqvEpuW7wPGvQyJvUiYZYqrirqm9mLrsNuWZgSPyHMop2J5j7+OW6P2Wn7h/k6JrdRvhh2Os+5SA6rIiajZHsr8Wbize6cvYTC3JjasbJ1Uka1dRyHhUZ+SYDMmsdLZZzffu/EZTd8Gas5/ZKqeE3ZNX2M+jY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wiesinger.com; spf=pass smtp.mailfrom=wiesinger.com; dkim=fail (4096-bit key) header.d=wiesinger.com header.i=@wiesinger.com header.b=HDGhkdFS reason="signature verification failed"; arc=none smtp.client-ip=46.36.37.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wiesinger.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=wiesinger.com Authentication-Results: smtp.subspace.kernel.org; dkim=fail reason="signature verification failed" (4096-bit key) header.d=wiesinger.com header.i=@wiesinger.com header.b="HDGhkdFS" Received: from wiesinger.com (wiesinger.com [84.112.177.114]) by vps01.wiesinger.com (Postfix) with ESMTPS id 2ED839F29F; Wed, 22 Jan 2025 08:29:11 +0100 (CET) Received: from [192.168.0.63] ([192.168.0.63]) (authenticated bits=0) by wiesinger.com (8.18.1/8.18.1) with ESMTPSA id 50M7T9SE205369 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 22 Jan 2025 08:29:10 +0100 DKIM-Filter: OpenDKIM Filter v2.11.0 wiesinger.com 50M7T9SE205369 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=wiesinger.com; s=default; t=1737530950; bh=YZE75MdPy5RhAMOEjpJvDDZapSIHxjRxf3GnH+3ns0A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=HDGhkdFS7vH/EIdvRTTxroSlPTvUO1rLeLVG0eRwLhxkY7YTbbMkvpmKHj5r7YoO1 Jp6WKPDZnulK1rQ36iwtEVslS/WUp7f/TTPa5DLjxIFAsJjJdtmBUXtKG7RhbLuyz9 uwd+e8b3c/tVPJXxDJpEU4gv6a8zj3dH1izOTa0v0ArPCNaZ8E58l0UkFgJ2s4BbON TpfTmtKRDFKTgMr3DV85hzgF5WHqFWHn7qat1KUL+/yq7b/jqoj2qznyrLwWs15gT4 K5RqNcu9XPBMPXu99lEpqy/u9gFU0y/1Q8DzTVS40XAPIXGvnPPUjl7tooHfioMh46 n+3dJuJsYKwYLXNDzAXu/m0VoiqZDERRTg01UGkrQtF16342EfeuvCv+JY53PBX9QW cMFz47fMlbgMD67VGlbVlX52BosyXOIHCCbg960GzdvFEIihQ+QIJY8VuAkjYSKh60 JTdkzvft7vxRRSYItk0CRnIKTTUMhYuJAg4byV3+xu6qzphL8+29rIvncVfQTfdIWe QbbF2M3MUXgKAqFctjJqpIlkTJmAipb5t0TW6GUxBZ7fPVJ6SZctE23tlvtESbHdK2 R81Asqy/orcf4QTGZ4n1cT6UNDuaVXoI2Q9BWpNWcYZJu6VeO0wBO8jicIm7k2+2ts EHBtFNR2w7ZS/i8cgXfNTBug= Message-ID: Date: Wed, 22 Jan 2025 08:29:09 +0100 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Betterbird (Windows) Subject: Re: Transparent compression with ext4 - especially with zstd Content-Language: en-US To: "Theodore Ts'o" Cc: linux-ext4@vger.kernel.org References: <8cb4d855-6bd8-427f-ac8f-8cf7b91547fb@wiesinger.com> <20250121040125.GC3761769@mit.edu> <213343dc-3911-45de-8195-469da9dd1a91@wiesinger.com> <20250121193351.GA3820043@mit.edu> From: Gerhard Wiesinger In-Reply-To: <20250121193351.GA3820043@mit.edu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 21.01.2025 20:33, Theodore Ts'o wrote: > On Tue, Jan 21, 2025 at 07:47:24PM +0100, Gerhard Wiesinger wrote: >> We are talking in some scenarios about some factors of diskspace. E.g. in >> my database scenario with PostgreSQL around 85% of disk space can be saved >> (e.g. around factor 7). > Worse, using a transparent compression breaks the ACID properties of > the database. If you crash or have a power failure while rewriting > the 64k compression cluster, all or part of that 64k compression > cluster can be corrupted. And if your customers care about (their) > data integrity, the fact that you cheaped out on disk space might not > be something that would impress them terribly. > BTW: Why does it break the ACID properties? Typically the transaction log will be (and have to be) flushed/synced to disk (fsync). If that's ok everything is fine and all DB transactions can be forwared if necessary. If that fails the last transaction is not recorded. I also don't see any compression related. That can also happen without compression. Any clarification? Ciao, Gerhard