From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mr001msb.fastweb.it ([85.18.95.85]:49808 "EHLO mr001msb.fastweb.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758564AbdKOSx5 (ORCPT ); Wed, 15 Nov 2017 13:53:57 -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 19:53:52 +0100 From: Gionatan Danti In-Reply-To: <20171115173100.GD5119@magnolia> References: <8b91c685e344bdc5d084b11fab1d50af@assyoma.it> <20171115173100.GD5119@magnolia> Message-ID: <434c9f876ca7fe93664419600e2e33a6@assyoma.it> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, g.danti@assyoma.it Il 15-11-2017 18:31 Darrick J. Wong ha scritto: > > I would evaluate these drives to find out if you really /can/ yank the > power without losing anything. If I can get some hard drives for testing, I'll surely do that. However, any in-house testing inevitably has limited scope and it can miss some important failure modes, so I am interested in other users' first-hand experience. > 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. From a point, I agree: I do not like black boxes. On the other hand, hardware RAID controllers *are* black boxes, and we all use them... > FWIW if the drive really /does/ have a non-volatile WC then a flush > should have nearly zero overhead. (Or so you'd think...) From my understanding (and I can be wrong), these drives honour cache flushes, with the associated performance drop. Ok, too much conjectures from my side, I think. I should *really* get my hand on some of these drives... 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