Date: Tue, 17 Aug 2004 15:44:04 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Wilko Bulte <wb@freebie.xs4all.nl> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src MAINTAINERS Message-ID: <41449.1092750244@critter.freebsd.dk> In-Reply-To: Your message of "Tue, 17 Aug 2004 15:27:40 %2B0200." <20040817132740.GA32139@freebie.xs4all.nl>
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In message <20040817132740.GA32139@freebie.xs4all.nl>, Wilko Bulte writes: >RAID-3 IIRC uses a dedicated parity disk, and small stripes. I don't think >it must be bytelevel striping. Just small enough stripes that all disks >contribute to every I/O RAID3 differs from RAID5 in that you always access the entire stripe and never have R/M/W cycles. Typically the problem is that by doing so you get a RAID3 sectorsize which is the sum of all non-parity sectors, a 4+1 will give you 4 x 512 = 2048 and 8 + 3 will give you 4k. Since a lot of filesystems/OS/hardware can only work with 512 byte sectors, people have hacked around this in various ways and eventually given up on RAID3. UFS/FFS works fine with 1k, 2k, 4k and larger sectorsizes and so RAID3 is a great idea for FreeBSD, and I'd rather use RAID3 than RAID5 myself. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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