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Date: Fri, 02 Dec 2005 15:05:30 -0500
To: "Rick Schumeyer" <rschumeyer@ieee.org>, <pgsql-performance@postgresql.org>
From: Ron <rjpeace@earthlink.net>
Subject: Re: two disks - best way to use them?
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At 01:58 PM 12/2/2005, Rick Schumeyer wrote:
>I installed another drive in my linux pc in an attempt to improve performance
>on a large COPY to a table with a geometry index.
>
>Based on previous discussion, it seems there are three things 
>competing for the hard drive:
>
>1)       the input data file
>2)       the pg table
>3)       the WAL
>
>What is the best way to distribute these among two drives?  From 
>Tom's comments
>I would think that the pg table and the WAL should be 
>separate.  Does it matter where the input data is?

Best is to have 3 HD or HD sets, one for each of the above.

With only 2, and assuming the input file is too large to fit 
completely into RAM at once, I'd test to see whether:
a=  input on one + pg table & WAL on the other, or
b= WAL on one + pg table & input file on the other
is best.

If the input file can be made 100% RAM resident, then use
c= pg table on one + WAL and input file on the other.

The big goal here is to minimize HD head seeks.

Ron