From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932238AbVJGGY0 (ORCPT ); Fri, 7 Oct 2005 02:24:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751381AbVJGGY0 (ORCPT ); Fri, 7 Oct 2005 02:24:26 -0400 Received: from web35507.mail.mud.yahoo.com ([66.163.179.131]:57178 "HELO web35507.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S1751380AbVJGGYZ (ORCPT ); Fri, 7 Oct 2005 02:24:25 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:Received:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=KltFuqe82Mcr3xDzlrFn6WIZgzyqcmNoOo8fY0jO9NJJc16Imn6MEUGdu6KehSQZHq1iqECWMoMSUL2nL8KrLjYr3U/FDCtEexPXJR8aNIUgmV8DxgYRB1fg6G1pX9O35mQRzMSmYDtVR5IBnd6cVVlkbX3cq8fgljyaxbZY79g= ; Message-ID: <20051007062425.56683.qmail@web35507.mail.mud.yahoo.com> Date: Thu, 6 Oct 2005 23:24:25 -0700 (PDT) From: Dan C Marinescu Subject: quick (software versus hardware raid) question (cpu) To: linux-kernel@vger.kernel.org In-Reply-To: <20051003112931.GA5209@opteron.random> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org hi there, i have a mission critical system with an unsuported raid controller (4 sata channels, sil 3114). so, i set up a software raid... now, the problem is at pick hours, when nics hardware interrupts compete with the software raid kernel thingie... i know you avoid spawning threads but regarless the scheduller's preeptivenes, the two kernel tasks are scheduller-wise competing and this is killing my server (slowing it down, cpu is at 100% user and 40-60% kernel). another issue is that not being able to "see" the "bios" partition (controller is totally unsuported) i cannot boot (unless i go like raid 1 on /boot). so what about performance? what about scalability? if case of 1 array (hardware raid) versus n distinct sata connectors, you big o notation goes like O(n) instead of O(1), no matter how smart the scheduller _is_ implemented, for the simple reason that hardware interrupts are hardware interrupts... preemptive or not, you have to serve them sooner or later and it's one thing to sever 1 instead of n... another issue is reliability. if you use software raid, and the kernel goes down (for unrelated reasons) your parity calculations and the raid cache go down as well, huh? and the other way around... the raid goes down, taking the sata driver with him... that takes the whole system down, huh? well, maybe i am too pesimistic but still, the scalability concern remains! nics are huge scheduller enamies... they have to do so much with cpu, and transfers to system memory, in order to actually server thier purpose (protocols) it seams to me that there isn't much left for user-land and software raid... (especially when many nics and many satas are involved...) in short, could you recommend me a peformant (sata connectors) raid controller, which is fully supported? please don't go like "make gconfig" cause i've been there... thanks! regards, daniel __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com