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Date:      Tue, 11 Mar 2003 10:36:21 -0500
From:      Chuck Swiger <cswiger@mac.com>
To:        freebsd Questions <freebsd-questions@FreeBSD.ORG>
Subject:   Re: Difference between Vinum and atacontrol RAID?
Message-ID:  <3E6E0275.2020408@mac.com>
In-Reply-To: <20030311032738.GB1912@bubba.toscano.org>
References:  <20030309233502.GC1899@bubba.toscano.org> <3E6BE734.4040804@mac.com> <20030311032738.GB1912@bubba.toscano.org>

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Pete wrote:
[ ... ]
> The RAID-1 volume I'm using right now is with two drives attached to
> a non-RAID card with a Promise chipset.

Does it work if you move the two drives to another machine without a 
Promise, Highpoint, or other RAID controller card or MB chipset...?

>> Hardware based RAID is likely to be faster, particularly in the case
>> of parity calculations for RAID-5.  (Not that many IDE controllers can
>> do RAID-5, but...)
>  
> It would be, but the RAID on the Promise and Highpoint devices is not
> true hardware RAID.  It's just software RAID with the drivers moved over
> to an EPROM on the card.

When you write to a RAID-1 mirror on such a device, does the CPU and PCI 
bus see two copies of the data?  Or does the Promise or HPT deal with 
distributing the data across the right devices itself?

 > I know from my own experience and that of
> other people that the Linux software RAID outperforms the "hardware"
> RAID of these devices.  I'm willing to bet that the FreeBSD RAID at
> least comes close, if not betters the Linux performance.

Software-based RAID can do fine for things like -0 & -1; but without 
numbers, subjective discussion of performance can be misleading....

-Chuck


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