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<p>Dear Tung-Han,<br>
</p>
<div class="moz-cite-prefix">Am 09.09.20 um 09:49 schrieb Tung-Han
Hsieh:<br>
</div>
<blockquote type="cite"
cite="mid:20200909074909.GA29604@twcp1.phys.ntu.edu.tw">
<pre class="moz-quote-pre" wrap="">Dear Robert,
Thank you very much for your prompt reply.
I have additional questions. Since we have a large Lustre file
system pool, some are OST with ldiskfs backend, and some are OST
with ZFS backend. Can I just enable compression on the ZFS backend
which is going to be joined into the Lustre file system without
affecting the remaining parts ?</pre>
</blockquote>
Maybe someone else can answer that. Our system runs exclusively on
ZFS backends (OST+MDT). I think it is not a problem to mix backends,
but I'm not sure and I never tried.<br>
<blockquote type="cite"
cite="mid:20200909074909.GA29604@twcp1.phys.ntu.edu.tw">
<pre class="moz-quote-pre" wrap="">
If my OST with ZFS has run for a while without compression enabled,
could I enable it without hurting the existing data ?</pre>
</blockquote>
<p>Yes. If you set compression=on, then new data will be compressed
(with LZ4), old data remains unchanged. If you turn compression
off again, then new data will not be compressed anymore. But data
already in the system remains compressed. This is the normal ZFS
behavior. Moving data with lfs migrate to an OST with compression
enabled will result in compressed data.<br>
</p>
<p>Cheers,<br>
Robert<br>
</p>
<blockquote type="cite"
cite="mid:20200909074909.GA29604@twcp1.phys.ntu.edu.tw">
<pre class="moz-quote-pre" wrap="">
Thank you very much.
T.H.Hsieh
On Wed, Sep 09, 2020 at 08:32:30AM +0200, Robert Redl wrote:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Dear Tung-Han,
you can use Lustre with ZFS backend and enabled compression. That has
the effect you are looking for and works very well.
Cheers,
Robert
Am 09.09.20 um 05:13 schrieb Tung-Han Hsieh:
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Dear All,
I would like to ask whether Lustre file system has implemented the
function to optimize for large sparse data files ?
For example, a 3GB data file but with more than 80% bytes zero, can
Lustre file system optimize the storage not actually taking the whole
3GB of disk space ?
I know that some file systems (e.g., ZFS) has this function. If Lustre
does not have it, is there a roadmap to implement it in the future ?
Thanks for your reply in advance.
Best Regards,
T.H.Hsieh
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</blockquote>
<div class="moz-signature">-- <br>
<p style="color:#808080;font-size:smaller">
Dr. Robert Redl<br>
Scientific Programmer, "Waves to Weather" (SFB/TRR165)<br>
Meteorologisches Institut<br>
Ludwig-Maximilians-Universität München<br>
Theresienstr. 37, 80333 München, Germany<br>
Tel.: +49 89 2180 4569
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