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From: Greg Smith <gsmith@gregsmith.com>
To: James Mansion <james@mansionfamily.plus.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Effects of setting linux block device readahead size
Date: Thu, 11 Sep 2008 01:56:40 -0400 (EDT)
Message-ID: <Pine.GSO.4.64.0809110150070.3993@westnet.com> (raw)
In-Reply-To: <48C8AACD.5090702@mansionfamily.plus.com>
References: <70c01d1d0809092353r4ae687a3ycf3d99d43a5680cf@mail.gmail.com>
	<Pine.GSO.4.64.0809101023520.15181@westnet.com>
	<a1ec7d000809100926w28a4a57dy7c13f2942edc57ff@mail.gmail.com>
	<Pine.GSO.4.64.0809101313070.4714@westnet.com>
	<48C8AACD.5090702@mansionfamily.plus.com>

On Thu, 11 Sep 2008, James Mansion wrote:

> Most spinning disks now are nearer to 100MB/s streaming.  You've talked 
> yourself into twice that, random access!

The point I was trying to make there is that even under impossibly optimal 
circumstances, you'd be hard pressed to blow out the disk's read cache 
with seek-dominated data even if you read a lot at each seek point.  That 
idea didn't make it from my head into writing very well though.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD



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