From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yan Seiner Subject: Re: Port multiplier resets Date: Wed, 19 Nov 2008 19:05:52 -0800 Message-ID: <4924D410.3030901@seiner.com> References: <490DC300.40703@seiner.com> <49194B20.8000209@kernel.org> <49242D9E.4050500@seiner.com> <4924CB05.9060100@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from flatoutfitness.com ([66.178.130.209]:44999 "EHLO www.seiner.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752195AbYKTDFx (ORCPT ); Wed, 19 Nov 2008 22:05:53 -0500 In-Reply-To: <4924CB05.9060100@kernel.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: linux-ide@vger.kernel.org Tejun Heo wrote: > Yan Seiner wrote: > >> Sorry for the delayed response. I've installed another controller based >> on the SiI 3132 chipset. The esata array is the same; I've simply moved >> the esata cables to the new controller. My observations: >> >> 1. The JMicron 20360/20363 AHCI Controller (rev 03) controller is far, >> far slower. hdparm clocks it at 20 mb/sec and a raid check takes about >> 15 hours. >> > > Hmm... That's probably due to lack of FIS based switching support. > The hardware (20360/3) can't do it and ahci doesn't support it yet > either. So, only commands to one drive can be in flight at any given > moment which is usually pretty bad for RAID. > So is there hope that FIS switching will make it into the driver or is this a hardware limitation? I have some time (months if not a year or two) before I really start to populate my external disk pack. (I have 20 slots with 4 - 5 port multipliers.) > >> 2. The JMicron controller experiences the above errors. >> > > Have you tried forcing the link speed? > Not yet. I spent the weekend building a remote switch and driver for the esata drive box. (Long story; I need to be able to shut the external drive pack off via software.) I need to check the drives as well make sure that the drives are not jumper-limited to 1.5 gb/sec. (one of those DUH! moments...) > >> 3. The Sil 3132 controller is faster. hdparm says 110 mb/sec and a >> raid check takes about 5 hours. This is confirmed by usage - I can >> stream 2 videos, record 2 videos, and commercial flag a video in myth >> with no visible stuttering. The JMicron controller stutters even with a >> single video streaming and recording. >> > > As said above, if you're running RAID on top of it, command based > switching will hurt bad. And 110Mb/s is about the limit of sil3132. > I'm OK with the speed of the sil controller. I'm concerned about the slow speed of the jmicron controller - it's about 1/3 to 1/5 as fast. > >> 4. The Sil 3132 controller doesn't have any errors even under high load. >> >> Google says the rev 3 version of the JMicron controller has these >> issues, and to turn off NCQ on it. It also indicates that these >> problems should have been resolved in my kernel - version 2.6.27.4 - but >> apparently not. :-( >> > > Nah.. I'm not aware of any such problem and it will work fine w/o PMP. > JMB ahci's are actually pretty good. Lack of FIS switching support > hurts when you use PMP tho. > > >> Is there a way to turn off NCQ on that controller without impacting the >> Sil 3132 controller? Any other things to try? >> > > You can do that with libata.force param but if you wanna put parallel > high load to the drives connected through PMP, no matter what you do, > the performance is gonna be bad if FIS switching is not supported. > > OK, thanks. I'll check the drive jumpers and see about setting the lower speed. The drives are used for storing and streaming videos. The idea is to have 4 esata channels, eventually with 5 sets of raid-5 arrays. Each raid-5 array consists of 4 drives, and each drive is on its own esata controller. The likelihood of multiple raid arrays being used at the same time is small, so I hope I won't get hit too bad performance-wise. Even if they get hit, the bandwidth is small; each video stream is about 8gb/hour. I'm waiting on more hardware (the esata cables, of all things) before I can test this out fully.