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Re: How many people regularly defrag their XFS filesystems?

To: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Subject: Re: How many people regularly defrag their XFS filesystems?
From: Chris Wedgwood <cw@xxxxxxxx>
Date: Sun, 26 Mar 2006 16:58:34 -0800
Cc: KELEMEN Peter <Peter.Kelemen@xxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <Pine.LNX.4.64.0603260917001.17017@p34>
References: <Pine.LNX.4.64.0603251848140.15947@p34> <20060326114503.GA15588@inara.maison.net> <Pine.LNX.4.64.0603260917001.17017@p34>
Sender: linux-xfs-bounce@xxxxxxxxxxx
On Sun, Mar 26, 2006 at 09:18:28AM -0500, Justin Piszcz wrote:

> Does anyone have any benchmarks for the XFS filesystem contrasted
> with the amount of fragmentation on the disk?  I have spoken with
> someone who believes defragmenting filesystems with XFS is probably
> a waste of time unless there are benchmarks to back it up.

it depends, badly fragmented files do hurt performance if it's
pathalogically bad, i've worked with a couple of people who do real
time video to help reduce this and the differences can be enourmous

> Benchmarks that show that performance degrades significantly as
> fragmentation increases.

benchmarks are highly subjective to the usage pattern and the job at
hand, so you need to state what you are trying to measure here in
more details

> Has anyone seen or performed any benchmarks? Is it worth defragging
> XFS filesystems?

again, it really depends, for some people it is a win, for many people
i doubt it's worth it

also, right now i'm a little concerned that there is some odd
interaction with one of my systems and xfs_fsr, if i copy several
hundred GBs of data to another volume and then run xfs_fsr afterwards
i will get the odd (md5) checksum mismatch --- i've not had a chance
to figure out why the odd file breaks but the bulk are ok though


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