Date: Mon, 7 Oct 1996 23:01:22 -0700 (PDT) From: asami@freebsd.org (Satoshi Asami) To: pjchilds@imforei.apana.org.au Cc: bsdscsi@shadows.aeon.net, freebsd-scsi@freebsd.org Subject: Re: striping/mirroring? Message-ID: <199610080601.XAA01024@silvia.HIP.Berkeley.EDU> In-Reply-To: <199609290943.TAA22973@al.imforei.apana.org.au> (message from Peter Childs on Sun, 29 Sep 1996 19:13:18 %2B0930 (CST))
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* From: Peter Childs <pjchilds@imforei.apana.org.au> * A fairly generic example of this would be a machine with a dual * SCSI bus system, a small system drive for root and /usr, and then * you data spread over say 4 2gb disks. * * So you would have * * SCSI BUS 1 SCSI BUS 2 * | | * +--> disk 1 +--> disk 3 * | | * +--> disk 2 +--> disk 4 * * Disk 1 and 2 would form a large interleaved data disks, which would * then be mirrored onto disk's 3 and 4. Actually, it would be better if you write your ccd.conf entry as ccd0 <interleave> CCDF_MIRROR disk1 disk3 disk2 disk4 That would make disk1 and disk3 the data disks and disk2 and disk4 the mirrors. Reads only come from the first half, so we want to spread those between both controllers. * Advantages are reasonable speed, and a measure of safety. If one disk * fails then you can just "turn-off" ccd and continue on with the other * good pair of disks. Yes...but I would recommend you keep at least one spare disk that you can substitute as soon as you find out you have a bad disk. (Ideally, this spare disk should be already connected so you can immediately start your recovery procedure.) Use "dd" to make a copy of the whole disk. Satoshi
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