From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maurice Hilarius Subject: Re: Awful RAID5 random read performance Date: Tue, 02 Jun 2009 09:14:39 -0600 Message-ID: <4A2541DF.40505@harddata.com> References: <20090601045710141.GMHE24335@cdptpa-omta04.mail.rr.com> <200905312339.12234.tfjellstrom@shaw.ca> <4A23CCF0.7030104@harddata.com> <7a329d910906020757vec0de52xb6b7e4557e82c489@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <7a329d910906020757vec0de52xb6b7e4557e82c489@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Wil Reichert Cc: tfjellstrom@shaw.ca, linux-raid@vger.kernel.org List-Id: linux-raid.ids Wil Reichert wrote: > On Mon, Jun 1, 2009 at 5:43 AM, Maurice Hilarius wrote: > >> Thomas Fjellstrom wrote: >> >>> .. >>> Yet I've heard NCQ makes some things worse. Some raid tweaking pages tell >>> you to try disabling NCQ. >>> >>> >> Not so relevant here. >> This recommendation to disable drive NCQ is generally due tot he fact that >> NCQ implementations by various manufacturers tend >> to differ in behaviour, and, in some cases , is just plain "broken". >> > > Not trying to start a flamewar on whos hardware is better, but I'd > love to get clarification on that last statement. I've always been > under the impression Intel gets their NCQ right (works for me). All > the reviews I've read on the current set of AMD southbridges indicate > they don't but I've no personal experience there. No idea about > nvidia or the cheap add-in sata cards like Silicon Image. > > Wil > From speaking with hardware RAID card manufacturers support engineers over the past few years, there have been several instances where NCQ implementations were incomplete, or faulty, or both. This seems to have improved a lot over the last year or two, so I think it is likely now "OK". However, from the earlier history I think there is a tendency for people now to assume it is "broken", and to turn it off. -- Regards, Maurice