From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ishtar.tlinx.org ([173.164.175.65]:45858 "EHLO Ishtar.hs.tlinx.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752442AbbL0AQl (ORCPT ); Sat, 26 Dec 2015 19:16:41 -0500 Message-ID: <567F2677.7040304@tlinx.org> Date: Sat, 26 Dec 2015 15:44:55 -0800 From: Linda Walsh MIME-Version: 1.0 To: Christoph Hellwig CC: Linux Block mailing list , XFS mailing list , Linux FS-Devel Subject: Re: XFS and nobarrier with SSDs References: <3496214.YTSKClH6pV@merkaba> <566E6524.6070401@xortex.com> <3911767.qVqsL1TcMv@merkaba> <20151214095823.GA30662@infradead.org> <566E978E.2070502@xortex.com> <20151214102750.GA29192@infradead.org> In-Reply-To: <20151214102750.GA29192@infradead.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Christoph Hellwig wrote: > The rule of thumb is: if nobarrier makes your workload run faster you > should not be using it, aka: don't use it. ---- So what is the purpose of the switch if it is to only be used when it makes no difference? I.e. My raid controller does write-through if it's internal battery needs replacing, otherwise, it does write-back. On top of that my system is on a UPS that is good for a hour or more of running. So, I used to use nobarrier on "work" disks where there were likely to be alot of "writes". Those disks are also backed up daily via xfsdump/restore. I figured those would benefit most, and at worst I could restore to previous morning's backup. Eventually stopped using the option, as for the most part, I couldn't really measure any reliable difference in performance (which means I should use it?!?). Hmmm... The only times I have experienced disk corruption on a single disk were either back before I ever tried the option, or when I had several months to a year where I tried to use software RAID5 (several-10+ years ago, before it was possible to use multiple cores for doing some RAID operations). I doubt I'm going to try it again soon, but being told that it's only "ok" to use an option when it makes no difference in performance *sounds* more than a little confusing.