From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: MD/RAID time out writing superblock Date: Fri, 18 Sep 2009 00:47:44 +0900 Message-ID: <4AB25A20.3040103@kernel.org> References: <20090916222842.GB16053@arachsys.com> <4AB17905.90606@kernel.org> <4AB23B17.2040204@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:39682 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755203AbZIQPsa (ORCPT ); Thu, 17 Sep 2009 11:48:30 -0400 In-Reply-To: <4AB23B17.2040204@rtr.ca> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Mark Lord Cc: Chris Webb , Ric Wheeler , Andrei Tanas , NeilBrown , linux-kernel@vger.kernel.org, IDE/ATA development list , linux-scsi@vger.kernel.org, Jeff Garzik , Mark Lord Hello, Mark Lord wrote: >> That's interesting. One important side effect of issuing IDENTIFY is >> that they will serialize command streams as they are not NCQ commands >> and thus could change command patterns significantly. > .. > > SMART is the opcode that is most frequently implicated here, not IDENTIFY. Yeap, any non-NCQ commands would do it. > Note that even a barrier FLUSH CACHE is non NCQ and will serialize > the stream. Yeah, I was just thinking that issuing non-NCQ commands mixed with NCQ commands would make the command stream fluctuate more. Modern drives are pretty good at lowering power consumption while idle so being more fluctuative (is it a word?) might have something to do with the problem. Just a wild speculation tho. Thanks. -- tejun