Date: Tue, 30 Apr 2002 10:15:49 -0700 From: Michael Sierchio <kudzu@tenebras.com> To: "James F.Hranicky" <jfh@cise.ufl.edu> Cc: Terry Lambert <tlambert2@mindspring.com>, bsder@allcaps.org, freebsd-fs@freebsd.org Subject: Re: Non-standard root filesystems Message-ID: <3CCED145.6010607@tenebras.com> References: <20020429153020.Q16532-100000@mail.allcaps.org> <3CCEC7D5.D22356A0@mindspring.com> <20020430130128.11428802.jfh@cise.ufl.edu>
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James F.Hranicky wrote: > "Terry Lambert" <tlambert2@mindspring.com> wrote: > >>As far as software RAID is concerned: it's a bad idea, from a >>performance perspective; I don't recommend it. Note that I'm >>the person who did the original user space RAIDframe port to >>FreeBSD in the mid 1990's, so I'm not just talking out my butt: >>the amount of overhead for parity calculation and storage is >>*considerable*, and makes RAID hardware a *much* better idea. > > > Perhaps with RAID 5, but with 0+1 using vinum, wouldn't you > see an increase with long enough plexes? > > Granted, it's more disks, but it may be cheaper than hardware RAID > (or not, haven't looked in a while). > > Plus, just a simple two disk mirror for / wouldn't be all that bad, > considering / shouldn't get heavy write traffic, right? It's true that RAID 5 is costlier on writes than RAID 1, but the problem with the comparison between software and hardware RAID is that the differences are revealed when other-than-normal operation is in force. It's really quite something to see mirror catch-up or parity recalculation on an entire disk because of crash or replacement -- when under something like Veritas or Vinum -- might as well take the system offline. "Cheaper than hardware RAID" depends on your metric, I suppose -- if the initial cost is all you're interested in, it's cheaper. Presumably folks use RAID because they're motivated by other concerns. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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