From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Port multiplier resets Date: Thu, 20 Nov 2008 12:23:28 +0900 Message-ID: <4924D830.8010103@kernel.org> References: <490DC300.40703@seiner.com> <49194B20.8000209@kernel.org> <49242D9E.4050500@seiner.com> <4924CB05.9060100@kernel.org> <4924D410.3030901@seiner.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:56004 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751818AbYKTDXk (ORCPT ); Wed, 19 Nov 2008 22:23:40 -0500 In-Reply-To: <4924D410.3030901@seiner.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Yan Seiner Cc: linux-ide@vger.kernel.org Yan Seiner wrote: > 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.) 20360/3 don't support them in hardware but there are controllers which do and ahci driver will be updated to support them. >> 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. Yeah, that's the difference coming from FIS and command based switching. > OK, thanks. I'll check the drive jumpers and see about setting the > lower speed. No, you don't have to do that. You can just use libata.force parameter. ie. if the JMB one is ATA host 3, you can say libata.force=3:1.5Gbps. -- tejun