From owner-freebsd-questions@FreeBSD.ORG Sun Apr 26 13:24:21 2009 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7A656106566B for ; Sun, 26 Apr 2009 13:24:21 +0000 (UTC) (envelope-from mkhitrov@gmail.com) Received: from mail-gx0-f170.google.com (mail-gx0-f170.google.com [209.85.217.170]) by mx1.freebsd.org (Postfix) with ESMTP id 0AB1F8FC14 for ; Sun, 26 Apr 2009 13:24:20 +0000 (UTC) (envelope-from mkhitrov@gmail.com) Received: by gxk18 with SMTP id 18so1378285gxk.19 for ; Sun, 26 Apr 2009 06:24:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :from:date:message-id:subject:to:cc:content-type :content-transfer-encoding; bh=0oQn+syBx2slwdegljVeZFhfxeDE7m/Hya+CGxmc+UU=; b=jPq8cHB1lkea2HIOlXwszsjW1iYpoNiHdrWBFDtvncincqaoMsKeF1YMKsaKih5/2S RidEXAyg5R8kmjxVARqHDxY6Kq5Jo8JQauRdoHN5I2NrvZ9Nf2gQcavyijIMmoSolJ3P mY3d/+wZcJUlakftFrqc1CmMqcrCTGfDRB0Ew= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:content-transfer-encoding; b=c+O5yDsmJVZu49RSAuE5QWPjY1QwXg8nHSvCtu55lptxKnJI1eYCHFTDn1kcLjeifI LeSJCvTfVFzcyV0NvOUoTI55NUUoRR6KrSKKNeqpia2px5WSY67RH6WO+GKU+TFD3MDo aBQxnDkGgDVfr8Suewvt+70RompdfsKCMtw34= MIME-Version: 1.0 Received: by 10.90.91.6 with SMTP id o6mr5550454agb.89.1240752260207; Sun, 26 Apr 2009 06:24:20 -0700 (PDT) In-Reply-To: References: <26ddd1750904251031q486a6ddar523d1470ce1fd8be@mail.gmail.com> From: Maxim Khitrov Date: Sun, 26 Apr 2009 09:24:05 -0400 Message-ID: <26ddd1750904260624x15edd57cub17812ea600357cd@mail.gmail.com> To: Wojciech Puchar Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Free BSD Questions list Subject: Re: Software raid5 through a sata port multiplier X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 26 Apr 2009 13:24:21 -0000 On Sat, Apr 25, 2009 at 6:02 PM, Wojciech Puchar wrote: >> thinking that a software raid5 solution may not be such a bad idea. > > software raid5 isn't any more bad than hardware raid5 most cases. > > just raid5 is bad if you use it in ANY type of load except: > > a) mostly reads - then set LARGE RAID stripe size > b) mostly huge files - then set small RAID stripe size to have highest > single thread transfer, or large to have higher concurency. > > EVERY OTHER case is bad case for RAID5 - just remember small write on > RAID5=2 reads+2 writes on disks. True, but aren't both steps done in parallel? So a single-disk equivalent is actually just one read for every write. >> The question is what port multiplier hardware does FreeBSD 7 support? > > it unfortunately doesn't. but your hardware RAID controllers drive disks by > itself and presents virtual drives to system, and system has nothing to do > with it. > so ask manufacturer if it supports port multipliers. The reason I don't want to depend on a hardware implementation is because this "server" is actually a shuttle xpc box, so not exactly built for reliability. If something breaks, I have to be able to move the disks to any other FreeBSD 7 machine and continue accessing the data. So I really just need some PCIe card and an external enclosure that will expose all attached disks to the operating system. From there I will determine how to arrange them, but I'd rather not have any controller that abstracts away the physical hard drives. - Max