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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 EE12CC10F06 for ; Sun, 31 Mar 2019 22:45:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B83CD20870 for ; Sun, 31 Mar 2019 22:45:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731406AbfCaWpy (ORCPT ); Sun, 31 Mar 2019 18:45:54 -0400 Received: from fieldses.org ([173.255.197.46]:34514 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731172AbfCaWpy (ORCPT ); Sun, 31 Mar 2019 18:45:54 -0400 Received: by fieldses.org (Postfix, from userid 2815) id D30141EF6; Sun, 31 Mar 2019 18:45:53 -0400 (EDT) Date: Sun, 31 Mar 2019 18:45:53 -0400 To: Qu Wenruo Cc: Supercilious Dude , "linux-btrfs@vger.kernel.org" , Linux FS Devel , linux-block@vger.kernel.org Subject: Re: Is it possible that certain physical disk doesn't implement flush correctly? Message-ID: <20190331224553.GA17421@fieldses.org> References: <16edb2d0-ee41-908f-e0bf-5c27160ccff7@gmx.com> <948a62d3-aa3e-418e-00df-d73d4dbfb5a6@gmx.com> <4f5586f7-aef1-4e2a-2aee-5d040c023c68@gmx.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4f5586f7-aef1-4e2a-2aee-5d040c023c68@gmx.com> User-Agent: Mutt/1.5.21 (2010-09-15) From: bfields@fieldses.org (J. Bruce Fields) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Sat, Mar 30, 2019 at 09:24:37PM +0800, Qu Wenruo wrote: > > > On 2019/3/30 下午9:14, Supercilious Dude wrote: > > On Sat, 30 Mar 2019 at 13:09, Qu Wenruo wrote: > >> > >> If controller is doing so, it must have its own power or at least finish > >> flush when controller writes to its fast cache. > >> > > > > The controller has its own battery backup to power the DRAM cache, as > > well as flash storage to dump it onto in the exceedingly unlikely > > event that the battery gets depleted. > > > >> For cache case, if we have enough data, we could still find some clue on > >> the flush execution time. > >> > >> Despite that, for that enterprise level usage, it's OK. > >> > >> But for consumer level storage, I'm not sure, especially for HDDs, and > >> maybe NVMe devices. > >> > > > > How do you distinguish who is a who? Am I an enterprise or a consumer? > > Easy, price. :P > > To be honest, I don't really care about that fancy use case. > It's the vendor doing its work, and if something wrong happened, > customer will yell at them. > > I'm more interesting in the consumer level situation. The feature seems to be advertised as "power loss protection" or "enhanced power loss data protection". Which makes it sound like a data safety feature when really it's a performance feature. E.g. these are the Intel drives with "EPLDP": https://ark.intel.com/content/www/us/en/ark/search/featurefilter.html?productType=35125&0_EPLDP=True Last I checked there were some that weren't too expensive. --b.