Message-ID: <4B7366D2.6040308@2ndquadrant.com>
Date: Wed, 10 Feb 2010 21:09:22 -0500
From: Greg Smith <greg@2ndquadrant.com>
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To: david@lang.hm
CC: Scott Marlowe <scott.marlowe@gmail.com>,
	Jeff <threshar@threshar.is-a-geek.com>,
	Hannu Krosing <hannu@2ndquadrant.com>,
	Kevin Grittner <Kevin.Grittner@wicourts.gov>,
	pgsql-performance@postgresql.org, Albe Laurenz <laurenz.albe@wien.gv.at>
Subject: Re: Linux I/O tuning: CFQ vs. deadline
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david@lang.hm wrote:
> most of my new hardware has no problems with the old kernels as well, 
> but once in a while I run into something that doesn't work.

Quick survey just of what's within 20 feet of me:
-Primary desktop:  2 years old, requires 2.6.23 or later for SATA to work
-Server:  3 years old, requires 2.6.22 or later for the Areca card not 
to panic under load
-Laptops:  both about 2 years old, and require 2.6.28 to work at all; 
mostly wireless issues, but some power management ones that impact the 
processor working right too, occasional SATA ones too.

I'm looking into a new primary desktop to step up to 8 HT cores; I fully 
expect it won't boot anything older than 2.6.28 and may take an even 
newer kernel just for basic processor and disks parts to work.

We're kind of at a worst-case point right now for this sort of thing, on 
the tail side of the almost 3 year old RHEL5 using a 3.5 year old kernel 
as the standard for so many Linux server deployments.  Until RHEL6 is 
ready to go, there's little motivation for the people who make server 
hardware to get all their drivers perfect in the newer kernels.  Just 
after that ships will probably be a good time to do that sort of 
comparison, like it was possible to easily compare RHEL4 using 2.6.9 and 
RHEL5 with 2.6.18 easily in mid to late 2007 with many bits of 
high-performance hardware known to work well on each.

-- 
Greg Smith    2ndQuadrant   Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com  www.2ndQuadrant.com