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From: mika ruohotie <bsdscsi@shadows.aeon.net>
Message-Id: <199610080853.KAA03301@shadows.aeon.net>
Subject: Re: striping/mirroring?
To: asami@freebsd.org (Satoshi Asami)
Date: Tue, 8 Oct 1996 10:53:57 +0200 (EET)
Cc: pjchilds@imforei.apana.org.au, freebsd-scsi@freebsd.org
In-Reply-To: <199610080601.XAA01024@silvia.HIP.Berkeley.EDU> from Satoshi Asami at "Oct 7, 96 11:01:22 pm"
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> 
> 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.

does this work already? (i cant experiment yet, disks are on purchase
list i have to get signed before i get the disks)

and am i right assuming (some old post listed these) that 128 is the
interleave value that gives me most speed for reads?

question, do i have to mirror as many drives as i am striping? since i'd
rather strip to 3 and mirror to one... (living close to the edge... =) )

>  *  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.  

it's this simple? nothing lost? sounds cool... =)

> 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.

but if the spare is online, and running there's the chance it is broken
already... and since it just hangs there i would not know it until...

> Satoshi


mickey