From: Pavel Machek <pavel@suse.cz>
To: Vojtech Pavlik <vojtech@suse.cz>
Cc: Derek Vadala <derek@cynicism.com>,
Roy Sigurd Karlsbakk <roy@karlsbakk.net>,
linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
Tedd Hansen <tedd@konge.net>, Christian Vik <christian@konge.net>,
Lars Christian Nygaard <lars@snart.com>
Subject: Re: RAID-6 support in kernel?
Date: Tue, 4 Jun 2002 15:49:05 +0000 [thread overview]
Message-ID: <20020604154904.J36@toy.ucw.cz> (raw)
In-Reply-To: <Pine.LNX.4.33.0206031020290.30424-100000@mail.pronto.tv> <Pine.GSO.4.21.0206030213510.23709-100000@gecko.roadtoad.net> <20020603113128.C13204@ucw.cz>
Hi!
> > > It'll waste 9 drives, giving me a total capacity of 7n instead of 14n.
> > > And, by definition, RAID-6 _can_ withstand _any_ two-drive failure.
> >
> > This is certainly not true.
> >
> > Combining N RAID-5 into a stripe wastes on N disks.
> >
> > If you combine two it wastes 2 disks, etc.
> >
> > That is, for each RAID-5 you waste a single disk worth of storage for
> > partiy. I don't know what equation you're using where you get 9 drives
> > from.
>
> He was thinking "mirror", not "stripe". Mirror of 2 RAID-5 arrays (would
> be probably called RAID-15 (when there is a RAID-10 for mirrored stripe
> arrays)), can withstand any two disks failing anytime. Even more for
RAID-1 over two RAID-5s should withstand any three failures, AFAICS.
You could do RAID-5 over RAID-5. That should survive any 2 failures and
still be reasonably efficient.
Pavel
--
Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt,
details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.
next prev parent reply other threads:[~2002-06-04 20:05 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-02 23:01 Roy Sigurd Karlsbakk
2002-06-03 0:33 ` Derek Vadala
2002-06-03 8:24 ` Roy Sigurd Karlsbakk
2002-06-03 9:25 ` Derek Vadala
2002-06-03 9:31 ` Vojtech Pavlik
2002-06-03 14:52 ` Kasper Dupont
2002-06-03 14:55 ` Vojtech Pavlik
2002-06-04 12:49 ` Roy Sigurd Karlsbakk
2002-06-04 15:49 ` Pavel Machek [this message]
2002-06-04 22:27 ` Kasper Dupont
2002-06-05 9:36 ` Roy Sigurd Karlsbakk
2002-06-05 9:28 ` Roy Sigurd Karlsbakk
2002-06-05 2:51 ` jw schultz
2002-06-04 18:50 ` Bill Davidsen
2002-06-06 1:19 ` Derek Vadala
2002-06-06 8:28 ` Kasper Dupont
2002-06-03 7:35 ` Kasper Dupont
2002-06-03 8:28 ` Roy Sigurd Karlsbakk
2002-06-03 8:57 ` Kasper Dupont
2002-06-04 11:11 ` Allan Sandfeld
2002-06-04 12:51 ` Kasper Dupont
2002-06-04 13:58 ` Allan Sandfeld
2002-06-12 8:13 ` Kasper Dupont
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