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Re: Defragging XFS File Systems

To: Kenneth Emerson <kenneth.emerson@xxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: Defragging XFS File Systems
From: Stewart Smith <stewart@xxxxxxxxxxxxxxxx>
Date: Tue, 07 Jun 2011 15:48:05 +1000
In-reply-to: <BANLkTi=40mmE+DCbLcSWBwNQtWpP=N=tXw@xxxxxxxxxxxxxx>
References: <BANLkTi=40mmE+DCbLcSWBwNQtWpP=N=tXw@xxxxxxxxxxxxxx>
User-agent: Notmuch/0.5-215-g5143e5e (http://notmuchmail.org) Emacs/23.2.1 (x86_64-pc-linux-gnu)
On Mon, 6 Jun 2011 22:52:48 -0500, Kenneth Emerson <kenneth.emerson@xxxxxxxxx> 
> I hadn't given much thought to fragmentation of my TV recordings volume
> (XFS) until reading through some MythTV-users threads recently that
> mentioned how fragmented an XFS file system could become.  After running
> xfs_db, I found out that my fs appeared to be quite bad:

MythTV can end up with fragmentation on XFS due to an fsync() call that
attempts to work raound limitations in ext3.

Workarounds include:
- allocsize mount parameter
- patch mythtv source not to fsync (you could easily write a patch that
only did fsync if not xfs... I've been meaning to do this for
years... not enough hours in day).
- run mythbackend with libeatmydata, thus disabling the fsync

Stewart Smith

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