Message-Id: <48C90F58.EE98.0025.0@wicourts.gov>
Date: Thu, 11 Sep 2008 12:30:16 -0500
From: "Kevin Grittner" <Kevin.Grittner@wicourts.gov>
To: "Matthew Wakeling" <matthew@flymine.org>,
 "Kenneth Marshall" <ktm@rice.edu>
Cc: <pgsql-performance@postgresql.org>
Subject: Re: Choosing a filesystem
References: <48C94770.2090505@shopzeus.com>
	<alpine.DEB.1.10.0809111814130.4454@aragorn.flymine.org>
	<20080911172332.GP6714@it.is.rice.edu>
In-Reply-To: <20080911172332.GP6714@it.is.rice.edu>
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>>> Kenneth Marshall <ktm@rice.edu> wrote:
> On Thu, Sep 11, 2008 at 06:18:37PM +0100, Matthew Wakeling wrote:
>> On Thu, 11 Sep 2008, Laszlo Nagy wrote:
>>> So the basic system will reside on a RAID 1 array, created from two
SAS 
>>> disks spinning at 15 000 rpm. I will buy 10 pieces of Seagate
Barracuda 
>>> 320GB SATA (ES 7200) disks for the rest.
>>
>> That sounds good. Put RAID 1 on the pair, and RAID 1+0 on the rest.
It'll 
>> be pretty good. Put the OS and the WAL on the pair, and the database
on the 
>> large array.
>>
>> However, one of the biggest things that will improve your
performance 
>> (especially in OLTP) is to use a proper RAID controller with a 
>> battery-backed-up cache.
> 
> But remember that putting the WAL on a separate drive(set) will only
> help if you do not have competing I/O, such as system logging or
paging,
> going to the same drives. This turns your fast sequential I/O into
> random I/O with the accompaning 10x or more performance decrease.
 
Unless you have a good RAID controller with battery-backed-up cache.
 
-Kevin