From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: Why is O_DSYNC on linux so slow / what's wrong with my SSD? Date: Sat, 23 Nov 2013 18:01:32 -0500 Message-ID: <529133CC.4070904@gmail.com> References: <528CA73B.9070604@profihost.ag> <20131120125446.GA6284@infradead.org> <528CC36A.7080003@profihost.ag> <20131120153703.GA23160@thunk.org> <528CDD19.5060002@symas.com> <20131123203600.GA791@amd.pavel.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Theodore Ts'o , Chinmay V S , Stefan Priebe - Profihost AG , Christoph Hellwig , linux-fsdevel@vger.kernel.org, Al Viro , LKML , matthew@wil.cx To: Pavel Machek , Howard Chu Return-path: Received: from mail-qe0-f48.google.com ([209.85.128.48]:61071 "EHLO mail-qe0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756294Ab3KWXBf (ORCPT ); Sat, 23 Nov 2013 18:01:35 -0500 In-Reply-To: <20131123203600.GA791@amd.pavel.ucw.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 11/23/2013 03:36 PM, Pavel Machek wrote: > On Wed 2013-11-20 08:02:33, Howard Chu wrote: >> Theodore Ts'o wrote: >>> Historically, Intel has been really good about avoiding this, but >>> since they've moved to using 3rd party flash controllers, I now advise >>> everyone who plans to use any flash storage, regardless of the >>> manufacturer, to do their own explicit power fail testing (hitting the >>> reset button is not good enough, you need to kick the power plug out >>> of the wall, or better yet, use a network controlled power switch you >>> so you can repeat the power fail test dozens or hundreds of times for >>> your qualification run) before being using flash storage in a mission >>> critical situation where you care about data integrity after a power >>> fail event. >> Speaking of which, what would you use to automate this sort of test? >> I'm thinking an SSD connected by eSATA, with an external power >> supply, and the host running inside a VM. Drop power to the drive at >> the same time as doing a kill -9 on the VM, then you can resume the >> VM pretty quickly instead of waiting for a full reboot sequence. > I was just pulling power on sata drive. > > It uncovered "interesting" stuff. I plugged power back, and kernel > re-estabilished communication with that drive, but any settings with > hdparm were forgotten. I'd say there's some room for improvement > there... > > Pavel Hi Pavel, When you drop power, your drive normally loses temporary settings (like a change to write cache, etc). Depending on the class of the device, there are ways to make that permanent (look at hdparm or sdparm for details). This is a feature of the drive and its firmware, not something we reset in the device each time it re-appears. Ric