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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,LOTS_OF_MONEY,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 ECB8EC04AB3 for ; Wed, 29 May 2019 06:56:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB1D5208CB for ; Wed, 29 May 2019 06:56:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="sF4PTQsw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725895AbfE2G4v (ORCPT ); Wed, 29 May 2019 02:56:51 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:35340 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725882AbfE2G4v (ORCPT ); Wed, 29 May 2019 02:56:51 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=xy/XIwjmIFCgclxo6NMMP4he3jCcIbmaHoeiaUStrCw=; b=sF4PTQsw/jy7WWcotv36VJ99m 0DFf92y9jdX1377myhMyIx2nlEnwyzTkk+/dBhbvkFIXRlc/h/Mwves4DgPncCG9yrJ9YDTW1F0KJ mW93LBneSVfvDnxBIjHHx+57NsqZDWbs9p9qO68ESHqiACp6sKqbDqnpiVwKiblzPZf2K//sZ/Fe0 Kw7TPH8G5AgyVvO22xQWFhb3DZJRxm7hS1jigO2bN9xF8XENJGn/aYkHG+fx9TunI9gpzoDdrOkx9 nkswLu8Uh1Or256ibMJcIVJxzziMnwCC45FssQoDYGref4hEoU9xbHCFL6vRG8ROxlYRR62PWKA+A x5ODNWEcg==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1hVsVz-0003Qg-QI; Wed, 29 May 2019 06:56:47 +0000 Date: Tue, 28 May 2019 23:56:47 -0700 From: Christoph Hellwig To: Theodore Ts'o Cc: Sahitya Tummala , Andreas Dilger , linux-ext4@vger.kernel.org Subject: Re: fsync_mode mount option for ext4 Message-ID: <20190529065647.GA8405@infradead.org> References: <20190528032257.GF10043@codeaurora.org> <20190528034007.GA19149@mit.edu> <20190528034830.GH10043@codeaurora.org> <20190528131356.GB19149@mit.edu> <20190529040757.GI10043@codeaurora.org> <20190529052332.GB6210@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190529052332.GB6210@mit.edu> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, May 29, 2019 at 01:23:32AM -0400, Theodore Ts'o wrote: > If you have protection against sudden shutdown, then nobarrier is > perfectly safe --- which is to say, if it is guaranteed that any > writes sent to device will be persisted after a crash, then nobarrier > is perfectly safe. So for example, if you are using ext4 connected to > a million dollar EMC Storage Array, which has battery backup, using > nobarrier is perfectly safe. And while we had a few oddities in the past in general any such device will obviously not claim to even have a volatile write cache, so nobarrier or this broken proposed mount option won't actually make any difference.