From owner-freebsd-database Thu Apr 11 16:51: 8 2002 Delivered-To: freebsd-database@freebsd.org Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by hub.freebsd.org (Postfix) with ESMTP id EB59437B422 for ; Thu, 11 Apr 2002 16:50:22 -0700 (PDT) Received: by elvis.mu.org (Postfix, from userid 1061) id 7EB30AE165; Thu, 11 Apr 2002 16:50:22 -0700 (PDT) Date: Thu, 11 Apr 2002 16:50:22 -0700 From: David Drum To: FreeBSD DB List Subject: Re: Raid configuration Message-ID: <20020411235022.GA21045@elvis.mu.org> Mail-Followup-To: David Drum , FreeBSD DB List References: <20020329113017.L51218-100000@zoraida.natserv.net> <20020411180923.O56810@flake.decibel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020411180923.O56810@flake.decibel.org> User-Agent: Mutt/1.3.27i Sender: owner-freebsd-database@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Quoth Jim C. Nasby: > FWIW, RAID10 is not two seperate mirrors, it's a single volume. It's > either a mirror of two striped volumes (yuck), or a stripe of mirrored > volumes. The first description you give is RAID 0+1, the second is RAID 1+0. There is a difference. If a disk goes bad in a RAID 0+1, you've lost an entire mirror, because the whole stripe is gone. If a disk goes bad in a RAID 1+0, you've only lost one mirrored drive, and not a whole stripe. mirror +-------------+ |strpA strpB | |+----+ +----+| || 1a | | 1b || RAID 0+1 (a mirror (RAID 0) of striped (RAID 1) drives) || | | || || 2a | | 2b || If one disk in the "a" stripe goes bad, the whole stripe || | | || is lost. So no matter how many disks are in the RAID, || 3a | | 3b || the loss of one results in a practical loss of 50%. |+----+ +----+| +-------------+ stripe +-------------+ | mirror1 | |+-----------+| || 1a 1b || RAID 0+1 (a mirror (RAID 0) of striped (RAID 1) drives) |+-----------+| | mirror2 | If any one disk in any of the three mirrors goes bad, |+-----------+| the stripe is still preserved. || 2a 2b || |+-----------+| | mirror3 | |+-----------+| || 3a 3b || |+-----------+| +-------------+ Regards, David Drum david@mu.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-database" in the body of the message