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Re: cannot defrag volume, fragmentation factor 21.73%

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: cannot defrag volume, fragmentation factor 21.73%
From: Richard Ems <richard.ems@xxxxxxxxxxxxxxxxx>
Date: Fri, 22 Oct 2010 12:12:27 +0200
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20101018231009.GL29677@dastard>
References: <4CBC3910.70806@xxxxxxxxxxxxxxxxx> <20101018231009.GL29677@dastard>
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20101013 SUSE/3.1.5 Thunderbird/3.1.5
On 10/19/2010 01:10 AM, Dave Chinner wrote:
Understand your numbers. What frag reports is how many extents there
are vs a perfect layout. It does not tell you how badly fragmented
your filesystem is. Extent-based filesystems can have
"fragmentation" like you see reported above, but not suffer at all
because the extents are large enough not to affect IO throughput.

Hi Dave,

I think I almost got that now.
But, at which numbers should I look at before starting a defrag then?

Up to now, I ran always "echo frag | xfs_db -r /dev/..." to get a "number" that could tell me if starting a xfs_fsr was necessary.

At which other numbers should I look at to see if running a xfs_fsr defrag is necessary or not?

Many thanks,

Richard Ems       mail: Richard.Ems@xxxxxxxxxxxxxxxxx

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