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From: Charles Swiger <cswiger@mac.com>
Date: Mon, 19 Jun 2006 11:57:15 -0400
To: Ensel Sharon <user@dhp.com>
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Cc: FreeBSD Mailing List <freebsd-questions@freebsd.org>
Subject: Re: Please help - adaptec 2820sa not ... RESOLVED
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On Jun 18, 2006, at 10:44 PM, Ensel Sharon wrote:
> Let's say I have 8 disks.
>
> Let's say I require raid6.

You require RAID-6 because...?  If you want more fault tolerance or  
better performance, RAID-10 makes a lot more sense to me than RAID-6,  
but YMMV.

> If I make one array, I lose 25% to raid overhead.
>
> If I make two arrays, I lose 50% to raid overhead.

Using RAID-6 with 4 disks does not make much sense, no.

(Using RAID-10 with 4 disks works great, however.  Yes, the overhead  
is greater, but the write performance is much better, and it would  
seem like RAID-10 would result in you having a configuration that  
fits into 2TB LUN limitation....)

-- 
-Chuck