From owner-freebsd-scsi@FreeBSD.ORG Sun Sep 21 09:19:54 2014 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 4EA14702 for ; Sun, 21 Sep 2014 09:19:54 +0000 (UTC) Received: from anubis.delphij.net (anubis.delphij.net [64.62.153.212]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "anubis.delphij.net", Issuer "StartCom Class 1 Primary Intermediate Server CA" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 3436FD3 for ; Sun, 21 Sep 2014 09:19:53 +0000 (UTC) Received: from delphij-macbook.local (unknown [106.120.42.90]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by anubis.delphij.net (Postfix) with ESMTPSA id 04F5219E6E; Sun, 21 Sep 2014 02:19:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=delphij.net; s=anubis; t=1411291193; x=1411305593; bh=KhdudE3yIwcqS8aHd02uR051f7EiBq17xxImiJFEICk=; h=Date:From:Reply-To:To:Subject:References:In-Reply-To; b=VWm1M3ErZy/MoFeZTUp4lRb6yN5Rr7vzr9LT5PruIIXUIuwrboRmSmALvmWHhFRSp LNUeIkAskzdHCodc8Vu/U7WBEEpN+obAPRYTKYi9YQaXpAklz7hGMrkxXnwhvSqDcV Io9Tx6ak1mkKGK1Z9hLFVuC3SBfMJDJVEELLAFuY= Message-ID: <541E9837.3060407@delphij.net> Date: Sun, 21 Sep 2014 17:19:51 +0800 From: Xin Li Reply-To: d@delphij.net Organization: The FreeBSD Project MIME-Version: 1.0 To: freebsd-scsi@freebsd.org Subject: Re: How to disable hard disk write cache? References: <541804B0.7070407@gmail.com> <54184484.1070304@delphij.net> <541E8DAE.8010407@gmx.de> <541E8F72.4020202@delphij.net> <541E91E4.4030802@gmx.de> In-Reply-To: <541E91E4.4030802@gmx.de> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 21 Sep 2014 09:19:54 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 9/21/14 4:52 PM, Matthias Andree wrote: > Am 21.09.2014 um 10:42 schrieb Xin Li: >> On 9/21/14 4:34 PM, Matthias Andree wrote: >>> Am 16.09.2014 um 16:09 schrieb Xin Li: >> >>>> Modern SATA/SAS/SCSI devices usually comes with the >>>> capability of tagged commands, allowing the OS to know when a >>>> write buffer is on stable storage. With this, file systems >>>> can easily implement the right semantics and recover from >>>> e.g. a power outage, etc. >> >>> Yes, they *can easily implement* that, but which file systems >>> in FreeBSD *actually do* that? >> >> Both UFS (with Soft Updates, which is what it's all about; I >> haven't checked the Journalled Soft Updates case) and ZFS do that >> for ages. > > Thank you. Is this in any of the 9.3 manpages so I could look that > up rather than ask questions on the lists? :-) I don't really know... I personally see it as a vital feature for any file systems (or otherwise they become the cat who ate our homework :) so I doubt if it's actually being explicitly documented. This is probably a good FAQ candidate though. Cheers, -----BEGIN PGP SIGNATURE----- iQIbBAEBCgAGBQJUHpg3AAoJEJW2GBstM+nsQDoP+IFrhCT+1LEfDOQYcC29XRi3 SHwrkoMOXgnvw0/h0xTGxQ9pLDl9xLIwTmaWdFNtHM1hYUI1XzZC96GuNSEQfxuR G6VPIsj6mb/sE0+HphZmJHsM3QG2gC9aiFtMr6DggBa4bWokFpjWIigmKP4z5eFD 9a+q4P5tZFIJUoKeDHEyxDdaoxXRWcD7528ALF7MueJXj0Ej1ErPdr4yAi63YUar VrqGqPSRnyEf5h/wak5UGy4ETXZmIScAONYDjI7bwZaJbgO/3qn3AqiV+xVtPJol EVW8b3LjMuV0/d+aym02eVqb4CMPx8JE2Zb8cPl9oVBI386ej9NKzVQVrbL9SC+N Ogm4ScYQxYBI6k7fKg7L2Iy9K2zYHAIdBSRlFjVRipn8O8wt8yrTq0lZYxLpykIY g1+lVeguKZtntF1jg0r4Bnw0+qhJczXf/Xu7icnWIcOjzcAKd+cIXjHzb/0Jh1ZN RM7hEyR7aHW5nwwZPfpV+Q5KWCflc9XgUxxWVVgzXkWDhDMuCpTSGBi/ohjbgPs7 I0cj4IBH+S7fTLuRrkYyUaUg3Sqe3Z3A9Tkyr2q4ePq6RctigcDjVHfbFNpL10b0 PQfF2IqprcMdGoiqIZoQ82qpwSNizFKVzv7vLQnWvFd2Fr3Gh2XQbXWESDo33QfR VMxnrmQ8xrfBxX2Bn9g= =ZkPk -----END PGP SIGNATURE-----