From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mr002msb.fastweb.it ([85.18.95.86]:46938 "EHLO mr002msb.fastweb.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753292AbdKOU1s (ORCPT ); Wed, 15 Nov 2017 15:27:48 -0500 Subject: Re: Disabling barriers on NVC-backed HDD MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Wed, 15 Nov 2017 21:27:21 +0100 From: Gionatan Danti In-Reply-To: References: <8b91c685e344bdc5d084b11fab1d50af@assyoma.it> <20171115173100.GD5119@magnolia> <20171115194700.GA6228@infradead.org> <442aa3b110e7cf10c8920dfe2159e41f@assyoma.it> Message-ID: 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 21:18 Gionatan Danti ha scritto: > Sorry, I forgot the link: > https://www.seagate.com/files/www-content/product-content/enterprise-performance-savvio-fam/enterprise-performance-15k-hdd/_cross-product/_shared/doc/enchanced-cache-advantage-tp691.1-1610us.pdf Ok, it seems that for Seagate drives the real document to read is that one[1]. Quoting: "When WCE=0, Advanced provides NVC-protected write caching over the portion of the DRAM used to coalesce writes. Write data only goes into NVC when there is an unexpected power loss to the drive. The NVC has 90-day data retention. When WCE=1, a Advanced Caching drive will operate on writes like a standard drive–writes in cache are not protected by NVC and may be lost with power loss." In short: - WCE=1 -> entire cache enabled -> powerloss = dataloss; - WCE=0 -> small write cache segment enabled -> powerloss = nodataloss. Unfortunately, I can not find anything on that regard about HGST's MediaCache... Regards. [1] https://www.seagate.com/www-content/product-content/enterprise-performance-savvio-fam/ent-perf-10k-hdd-v9-skybolt/en-us/docs/100818015c.pdf -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8