From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([65.50.211.133]:47330 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752629AbdKOTrD (ORCPT ); Wed, 15 Nov 2017 14:47:03 -0500 Date: Wed, 15 Nov 2017 11:47:00 -0800 From: Christoph Hellwig Subject: Re: Disabling barriers on NVC-backed HDD Message-ID: <20171115194700.GA6228@infradead.org> References: <8b91c685e344bdc5d084b11fab1d50af@assyoma.it> <20171115173100.GD5119@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171115173100.GD5119@magnolia> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" Cc: Gionatan Danti , linux-xfs@vger.kernel.org On Wed, Nov 15, 2017 at 09:31:00AM -0800, Darrick J. Wong wrote: > I would evaluate these drives to find out if you really /can/ yank the > power without losing anything. > > That said, if the manufacturers aren't willing to tell you how that > feature works, I'd just as soon pretend the feature didn't exist and > continue sending flushes to the drive. > > FWIW if the drive really /does/ have a non-volatile WC then a flush > should have nearly zero overhead. (Or so you'd think...) And in that case it will report WCE=0 and Linux won't even flush. As is the case for typical enterprise disks.