From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fieldses.org ([173.255.197.46]:36930 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752166AbeDRQwU (ORCPT ); Wed, 18 Apr 2018 12:52:20 -0400 Date: Wed, 18 Apr 2018 12:52:19 -0400 To: Martin Steigerwald Cc: "Theodore Y. Ts'o" , "Joshua D. Drake" , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: fsync() errors is unsafe and risks data loss Message-ID: <20180418165219.GC9897@fieldses.org> References: <8da874c9-cf9c-d40a-3474-b773190878e7@commandprompt.com> <20180410184356.GD3563@thunk.org> <14942494.44S1RI7MjI@merkaba> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <14942494.44S1RI7MjI@merkaba> From: bfields@fieldses.org (J. Bruce Fields) Sender: linux-fsdevel-owner@vger.kernel.org List-ID: > Theodore Y. Ts'o - 10.04.18, 20:43: > > First of all, what storage devices will do when they hit an exception > > condition is quite non-deterministic. For example, the vast majority > > of SSD's are not power fail certified. What this means is that if > > they suffer a power drop while they are doing a GC, it is quite > > possible for data written six months ago to be lost as a result. The > > LBA could potentialy be far, far away from any LBA's that were > > recently written, and there could have been multiple CACHE FLUSH > > operations in the since the LBA in question was last written six > > months ago. No matter; for a consumer-grade SSD, it's possible for > > that LBA to be trashed after an unexpected power drop. Pointers to documentation or papers or anything? The only google results I can find for "power fail certified" are your posts. I've always been confused by SSD power-loss protection, as nobody seems completely clear whether it's a safety or a performance feature. --b.