From owner-freebsd-hackers Fri Mar 24 10:23:26 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from mass.cdrom.com (mg134-072.ricochet.net [204.179.134.72]) by hub.freebsd.org (Postfix) with ESMTP id 9326237B71D for ; Fri, 24 Mar 2000 10:23:18 -0800 (PST) (envelope-from msmith@mass.cdrom.com) Received: from mass.cdrom.com (localhost [127.0.0.1]) by mass.cdrom.com (8.9.3/8.9.3) with ESMTP id KAA00964; Fri, 24 Mar 2000 10:26:22 -0800 (PST) (envelope-from msmith@mass.cdrom.com) Message-Id: <200003241826.KAA00964@mass.cdrom.com> X-Mailer: exmh version 2.1.1 10/15/1999 To: Zhihui Zhang Cc: freebsd-hackers@freebsd.org Subject: Re: Software RAID and vinum In-reply-to: Your message of "Fri, 24 Mar 2000 10:52:11 EST." Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Fri, 24 Mar 2000 10:26:22 -0800 From: Mike Smith Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > I searched the mailing list archive. I am not sure whether Vinum has > solved the problem of atomic writes in a stripe to both the data fragment > and parity fragment (RAID 5). In the case of a crash, you have no idea of > where the writes have finished (even worse, a fragment may contain > several sectors). This problem can't be solved with software-only RAID, and no (sensible) software RAID implementation attempts to deal with it. Software RAID reliability is predicated on the correct functioning of the system; it's there to provide fault tolerance for the high-failure-rate hardware (eg. disks). > If this problem is not easily solved in software, does it mean that only > hardware RAID can guarantee availability of data and software RAID can > only be used to increase performance? How about the Linux software RAID > support? Typically you work around this by using a hardware RAID adapter with battery-backed memory; you need nonvolatile storage to achieve the results you're looking for. -- \\ Give a man a fish, and you feed him for a day. \\ Mike Smith \\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org \\ and he'll hate you for a lifetime. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message