Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261205AbUDPBEL (ORCPT ); Thu, 15 Apr 2004 21:04:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261753AbUDPBEK (ORCPT ); Thu, 15 Apr 2004 21:04:10 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:7076 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S261205AbUDPBED (ORCPT ); Thu, 15 Apr 2004 21:04:03 -0400 Message-ID: <407F30F5.1070305@pobox.com> Date: Thu, 15 Apr 2004 21:03:49 -0400 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030703 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Simon Koch CC: Ryan Geoffrey Bourgeois , linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org Subject: Re: poor sata performance on 2.6 References: <200404150236.05894.kos@supportwizard.com> <1082001287.407e0787f3c48@webmail.LaTech.edu> <200404151455.36307.kos@supportwizard.com> <1082044297.407eaf894ddda@webmail.LaTech.edu> <407F1C07.6050104@umn.edu> In-Reply-To: <407F1C07.6050104@umn.edu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2104 Lines: 51 Simon Koch wrote: > Ryan Geoffrey Bourgeois wrote: >> I do recomend Promise's SATA controller cards. The kernel drivers are >> excellent >> imho. As well as my onboard Promise TX2, I'm using a thei S150 SX4 RAID5 > What kernel/driver are you using for the S150 SX4? I couldn't ever get > better than 13MB/sec from it in 2.6. Of course, the last I tried was > 2.6.3. I could get 55MB/sec using 2.4 and Promise's partial source > driver, but since my onboard SATA controller works fine in 2.6 I'm just > using that meanwhile. Re-read his message. He is using TX2, not SX4. SX4 is vastly different. Each request must bounce through a DIMM, which hurts performance. Further, only one DIMM copy to/from system memory can be occuring at any one time, while you can be executing up to 4 ATA commands (one for each SATA port) in parallel. SX4 performance currently suffers because of this bounce through the DIMM. Two transactions, and two interrupts, are required for each disk transaction. SX4 is really designed for RAID acceleration. One may to improve performance (which I plan to implement) is using the DIMM as a write-through cache. Another way to improve performance on SX4 is to have a special RAID driver which issues RAID1 or RAID5 reads and writes as a single transaction, thus maximizing the potential of the DIMM and cutting in _half_ the PCI bus bandwidth used for writes. SX4, like other Promise products, can also offload RAID5 XOR calculations onto the hardware. I _really_ like the SX4 -- it gives the programmer full control over all aspects of RAID operation, while providing useful hardware acceleration where it's needed. And not getting in the way of the programmer, when it's not needed. But currently, my libata driver does not use the advanced features, and so there is a performance hit. Jeff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/