Message-ID: <479F40EF.6070802@emolecules.com>
Date: Tue, 29 Jan 2008 07:06:23 -0800
From: Craig James <craig_james@emolecules.com>
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To: Mike Smith <mike.smith@enterprisedb.com>
CC: pgsql-performance@postgresql.org
Subject: Re: 8x2.5" or 6x3.5" disks
References: <285fb20801281125k641902feo8d74b1c68640d94b@mail.gmail.com>
	<51494DB187D98F4C88DBEBF1F5F6D42303EC56C9@edb06.mail01.enterprisedb.com>
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Mike Smith wrote:
> I’ve seen a few performance posts on using different hardware 
> technologies to gain improvements. Most of those comments are on raid, 
>  interface and rotation speed.   One area that doesn’t seem to have 
>  been mentioned  is to  run your disks empty.
> ...
> On the outside of the disk you get a lot more data per seek than on the 
> inside. Double whammy you get it faster.
> 
> Performance  can vary more than  100% between the outer and inner tracks 
> of the disk.   So running a slower disk twice as big may give you more 
> benefit than running a small capacity 15K disk full.  The slower disks 
> are also generally more reliable and mostly much cheaper.
> ...
> This is not very green as you need to buy more disks for the same amount 
> of data and its liable to upset your purchasing department who won’t 
> understand why you don’t want to fill your disks up.

So presumably the empty-disk effect could also be achieved by partitioning, say 25% of the drive for the database, and 75% empty partition.  But in fact, you could use that "low performance 75%" for rarely-used or static data, such as the output from pg_dump, that is written during non-peak times.

Pretty cool.

Craig