Date: Fri, 24 Mar 2000 10:26:22 -0800 From: Mike Smith <msmith@freebsd.org> To: Zhihui Zhang <zzhang@cs.binghamton.edu> Cc: freebsd-hackers@freebsd.org Subject: Re: Software RAID and vinum Message-ID: <200003241826.KAA00964@mass.cdrom.com> In-Reply-To: Your message of "Fri, 24 Mar 2000 10:52:11 EST." <Pine.GSO.3.96.1000324104133.1834A-100000@sol.cs.binghamton.edu>
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> > 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
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