Date: Sun, 12 May 2013 11:53:37 -0500
From: Rob Landley <rob@landley.net>
Subject: Re: high-speed disk I/O is CPU-bound?
To: David Oostdyk <daveo@ll.mit.edu>
Cc: linux-kernel@vger.kernel.org
References: <518CFE7C.9080708@ll.mit.edu>
In-Reply-To: <518CFE7C.9080708@ll.mit.edu> (from daveo@ll.mit.edu on Fri May
	10 09:04:44 2013)
Message-Id: <1368377617.18069.228@driftwood>
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On 05/10/2013 09:04:44 AM, David Oostdyk wrote:
> Hello,
> 
> I have a few relatively high-end systems with hardware RAIDs which  
> are being used for recording systems, and I'm trying to get a better  
> understanding of contiguous write performance.
...
> The question is, is it possible that high-speed I/O to these hardware  
> RAIDs could
> actually be CPU-bound above ~1400MB/sec?

In some setups your processor is calculating CRCs for the data. It's a  
fairly cheap operation, but a cheap operation on gigabytes of data can  
still saturate your memory bus.

Rob--
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