From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: SATA RAID5 speed drop of 100 MB/s Date: Sat, 23 Jun 2007 16:54:16 +0900 Message-ID: <467CD1A8.5070700@gmail.com> References: <20070620224847.GA5488@alinoe.com> <4679B2DE.9090903@garzik.org> <20070622214859.GC6970@alinoe.com> <467CC5C5.6040201@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from py-out-1112.google.com ([64.233.166.182]:44590 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752185AbXFWHyW (ORCPT ); Sat, 23 Jun 2007 03:54:22 -0400 Received: by py-out-1112.google.com with SMTP id u77so729656pyb for ; Sat, 23 Jun 2007 00:54:22 -0700 (PDT) In-Reply-To: <467CC5C5.6040201@garzik.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: Carlo Wood , Manoj Kasichainula , linux-kernel@vger.kernel.org, IDE/ATA development list Jeff Garzik wrote: > Carlo Wood wrote: >> The dmesg output of 33480a0ede8dcc7e6483054279008f972bd56fd3 (thus >> "before") is: > [...] >> And the dmesg output of 551c012d7eea3dc5ec063c7ff9c718d39e77634f (thus >> "after") is: > [...] > > Your disk configurations are quite radically different between the two > kernels (see attached diff for key highlights). > > The new behavior of the more recent kernel (551c012d7...) is that it now > fully drives your hardware :) The reset problems go away, NCQ is > enabled, and if you had 3.0Gbps drives (you don't) they would be driven > at a faster speed. > > Given that some drives might be better tuned for benchmarks in > non-queued mode, and that a major behavior difference is that your > drives are now NCQ-enabled, the first thing I would suggest you try is > disabling NCQ: > http://linux-ata.org/faq.html#ncq > > Other indicators are the other changes in the "ahci 0000:00:1f.2: > flags:" line, which do affect other behaviors, though none so important > to RAID5 performance as NCQ, I would think. > > Turning on NCQ also potentially affects barrier behavior in RAID, though > I'm guessing that is not a factor here. Ah.. right. That should have enabled NCQ. Me slow today. :-) -- tejun