Consistent throughput challenge -- fragmentation?

[Brian Cain]

On Mon, Feb 25, 2013 at 3:39 PM, Stan Hoeppner <stan at hardwarefreak.com>wrote:

> On 2/25/2013 10:01 AM, Brian Cain wrote:
> > All,
> >
> > I have been observing some odd behavior regarding write throughput to an
> > XFS partition (the baseline kernel version is 2.6.32.27).  I see
> > consistently high write throughput (close to the performance of the raw
> > block device) to the filesystem immediately after a mkfs, but after a few
> > test cycles, there is sporadic poor performance.
> >
> > The test mechanism is like so:
> >
> > [mkfs.xfs <blockdev>] (no flags/options, xfsprogs ver 3.1.1-0.1.36)
> > ...
> > 1. remove a previous test cycle's directory
> > 2. create a new directory
> > 3. open/write/close a small file (4kb) in this directory
> > 4. open/read/close this same small file (by the local NFS server)
> > 5. open[O_DIRECT]/write/write/write/.../close a large file (anywhere from
> > ~100MB to 200GB)
> >
>
>
It looks like omitting step #2 and putting all files in the root directory
(and modifying step #1 to remove only the files that were associated with
that previous test cycle) avoids the poor-performance problem as well.  At
least, that's the case in testing so far.

-- 
-Brian
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