From mboxrd@z Thu Jan 1 00:00:00 1970 From: One Thousand Gnomes Subject: Re: Why is O_DSYNC on linux so slow / what's wrong with my SSD? Date: Sun, 24 Nov 2013 01:03:16 +0000 Message-ID: <20131124010316.2ca6a8ce@alan.etchedpixels.co.uk> References: <528CA73B.9070604@profihost.ag> <20131120125446.GA6284@infradead.org> <528CC36A.7080003@profihost.ag> <20131120153703.GA23160@thunk.org> <528CDD19.5060002@symas.com> <20131123203600.GA791@amd.pavel.ucw.cz> <529133CC.4070904@gmail.com> <20131124002236.GA10600@amd.pavel.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Ric Wheeler , Howard Chu , "Theodore Ts'o" , Chinmay V S , Stefan Priebe - Profihost AG , Christoph Hellwig , linux-fsdevel@vger.kernel.org, Al Viro , LKML To: Pavel Machek Return-path: Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:41110 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755609Ab3KXBD5 (ORCPT ); Sat, 23 Nov 2013 20:03:57 -0500 In-Reply-To: <20131124002236.GA10600@amd.pavel.ucw.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: > Yes, and I'm arguing that is a bug (as in, < 0.01% people are using > hdparm correctly). Generally speaking if you are using hdparm for tuning it means we need to fix something in the ATA layer so you don't have to ! > I guess it would be safer not to reattach drives after power > fail... (also I wonder what this does to data integrity. Drive lost > content of its writeback cache, but kernel continues... Journal will > not prevent data corruption in this case). For good or bad its very hard to tell if a drive randomly powers off or we merely get a bus reset in the ATA case. In the SATA case we do at least get the relevant events to handle it nicely as we *should* see a DevExch event. We also can't tell a power fail event from a hot drive swap, so we most definitely want to re-attach the drive, just so long as we ensure that it comes back on a different device node. Alan