From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mr002msb.fastweb.it ([85.18.95.86]:42406 "EHLO mr002msb.fastweb.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753984AbdKOURp (ORCPT ); Wed, 15 Nov 2017 15:17:45 -0500 Subject: Re: Disabling barriers on NVC-backed HDD MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 15 Nov 2017 21:17:13 +0100 From: Gionatan Danti In-Reply-To: <20171115194700.GA6228@infradead.org> References: <8b91c685e344bdc5d084b11fab1d50af@assyoma.it> <20171115173100.GD5119@magnolia> <20171115194700.GA6228@infradead.org> Message-ID: <442aa3b110e7cf10c8920dfe2159e41f@assyoma.it> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Christoph Hellwig Cc: "Darrick J. Wong" , linux-xfs@vger.kernel.org, g.danti@assyoma.it Il 15-11-2017 20:47 Christoph Hellwig ha scritto: > And in that case it will report WCE=0 and Linux won't even flush. > As is the case for typical enterprise disks. Good point. Based on what I read here[1], page n.4, it *seems* that Seagate AWC (advanced write cache) enabled drives report WCD (write cache disabled) to the host OS. I think this is the key parameter to watch: if the HDD vendor is confident enough to report WCE=0/WCD, than it should be safe running without barriers (after all, in this case Linux *will* disable barrier by default). Thank you Christoph for pointing that. Regards. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8