Defragging XFS File Systems

[Stan Hoeppner]

On 6/9/2011 12:49 AM, Michael Monnerie wrote:
> On Mittwoch, 8. Juni 2011 Kenneth wrote:
>>> After that, I will make
>>> a cron job to run on a regular basis to keep the volume from
>>> getting so fragmented again.
> 
> How will you do that? Running xfs_fsr on a regular basis is *not* 
> recommended, as it will age your filesystem and defrag free space. In 
> the beginning, and as long as your filesystem is maybe 50% full it will 
> be fine, but there's a point where it starts to get worse - much worse. 
> Just run a recent kernel, it has all the naughty stuff to help keep the 
> performance high.

When *is* running xfs_fsr recommended?

I scheduled it twice a week some time ago due to a filesystem containing
active mbox files.  I did so because they became so heavily fragmented
in short order, especially those swallowing copious amounts of list
mail.  Before cron'ing xfs_fsr I was seeing mbox files with over 1000
fragmented extents, and increasing MUA latency as the files became more
fragmented.  The filesystem is currently 90% free.

-- 
Stan