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Date:      Mon, 05 Sep 2005 11:46:03 -0400
From:      Chuck Swiger <cswiger@mac.com>
To:        Jeff Tchang <jeff.tchang@gmail.com>
Cc:        freebsd-performance@freebsd.org
Subject:   Re: 3Ware 7500-4 Slow
Message-ID:  <431C683B.1080803@mac.com>
In-Reply-To: <63f9d26505090417183dff415e@mail.gmail.com>
References:  <63f9d26505090417183dff415e@mail.gmail.com>

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Jeff Tchang wrote:
[ ... ]
> When I attempt to write many small files or remove a directory is when the 
> slowness kicks in. Is this just something due to Raid5? Here is the output 
> of Bonnie++:

Small writes are pretty much the worst-case scenario for RAID-5, and it's 
normal to see a very significant performance drop-- by up to an order of 
magnitude-- from the performance of a bare drive.  Good RAID controllers with 
lots of RAM can reduce the performance hit to perhaps less than a factor of 2.

Choosing RAID-1 rather than RAID-5 for situations which are not read-only or 
read-mostly is probably a good idea.

-- 
-Chuck




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