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 <B6F6FD62F2624C4C9916AC0175D56D8828A9B485@jenmbs01.ad.intershop.net>
Message-ID: <1404324089.35659.YahooMailNeo@web122301.mail.ne1.yahoo.com>
Date: Wed, 2 Jul 2014 11:01:29 -0700
From: Kevin Grittner <kgrittn@ymail.com>
Reply-To: Kevin Grittner <kgrittn@ymail.com>
Subject: Re: fragmention issue with ext4: e4defrag?
To: Marc Mamin <M.Mamin@intershop.de>,
 "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
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Marc Mamin <M.Mamin@intershop.de> wrote:

> I/O througput decreased from 300MB/s to 160.

I don't have any experience with ext4 defrag tools, but just wanted
to point out that the difference in performance you cite above is
about the same as the difference between accessing data on the
outer (and usually first-filled) tracks on a disk drive and the
inner tracks.=A0 One of the reasons performance falls as a drive
fills is that the OS is compelled to use slower and slower portions
of the disk.=A0 Part of the benefit you are seeing might be due to
freeing "fast" tracks and data being relocated there.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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