From owner-freebsd-stable Tue Aug 26 22:30:05 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id WAA10104 for stable-outgoing; Tue, 26 Aug 1997 22:30:05 -0700 (PDT) Received: from MindBender.serv.net (root@mindbender.serv.net [205.153.153.98]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id WAA10048 for ; Tue, 26 Aug 1997 22:29:32 -0700 (PDT) Received: from localhost.HeadCandy.com (michaelv@localhost.HeadCandy.com [127.0.0.1]) by MindBender.serv.net (8.7.5/8.7.3) with SMTP id WAA25841; Tue, 26 Aug 1997 22:29:09 -0700 (PDT) Message-Id: <199708270529.WAA25841@MindBender.serv.net> X-Authentication-Warning: MindBender.serv.net: Host michaelv@localhost.HeadCandy.com [127.0.0.1] didn't use HELO protocol To: Tom cc: FreeBSD , stable@freebsd.org Subject: Re: DPT scsi card In-reply-to: Your message of Tue, 26 Aug 97 21:16:49 -0700. Date: Tue, 26 Aug 1997 22:28:42 -0700 From: "Michael L. VanLoon -- HeadCandy.com" Sender: owner-freebsd-stable@freebsd.org X-Loop: FreeBSD.org Precedence: bulk >On Tue, 26 Aug 1997, Michael L. VanLoon -- HeadCandy.com wrote: >> You can do RAID in software with the ccd (concatenated disk) driver. >> There are FreeBSD and NetBSD servers running this all over the place. >> It's rock solid extremely fast. > I wouldn't call ccd a RAID solution. The "R" in RAID stands for >redundant, and ccd has poor support for that. While that was the original "definition", RAID had become to be known for more than simple redudancy in common usage. Striping without fault tolerance is a very common usage, which generally falls under the term "RAID-5", if I'm not mistaken. >From what I understand, ccd can be used for mirroring. However, recovery in case of failure is not automatic, and you can't mix mirroring with striping. So, yes, if you're using ccd to stripe for performance, you don't get any redundancy features with ccd. If you use it for mirroring, it's likely that you won't get any performance benefits. DPT controllers are reported to do all that stuff transparently in hardware. And, the FreeBSD driver supports basic functionality on DPT cards. However, it isn't clear how much advanced functionality the FreeBSD DPT driver supports. ----------------------------------------------------------------------------- Michael L. VanLoon michaelv@MindBender.serv.net Contract software development for Windows NT, Windows 95 and Unix. Windows NT and Unix server development in C++ and C. --< Free your mind and your machine -- NetBSD free un*x >-- NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3, Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32... NetBSD ports in progress: PICA, others... -----------------------------------------------------------------------------