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<p>Patrick,</p>
<p>I am running a simple simulator program that writes sim.dat and
then reads sim.dat. The program then writes sim.dat.B and then
reads sim.dat.B forwards and backwards.</p>
<p>Each file is striped 3x16M. Each file is striped on 3 different
OST.</p>
<p><br>
</p>
<p>Without doing the stat()s from the front-end node the file
activity versus time plot looks like this.</p>
<p><br>
</p>
<p><img moz-do-not-send="false"
src="cid:part1.knJnE0FB.d4oI6hqu@iodoctors.com"
alt="https://www.dropbox.com/scl/fi/31oyih092digsfqcmyrzs/3440.fpa.png?rlkey=77lybqpyp4t7fu11ndhqe78qu&st=a8nf16tt&dl=0"
width="1052" height="683"></p>
<p><br>
</p>
<p><br>
</p>
<p>This next image is the amount of cached memory used by each of
the 3 OSC, on the compute node, versus time for the first file.
It looks like only one line, but all 3 OSC have the same memory
profile, so they are on top of each other.</p>
<p><br>
</p>
<p><img moz-do-not-send="false"
src="cid:part2.bXLf3aNt.jgoPvUgT@iodoctors.com"
alt="https://www.dropbox.com/scl/fi/1n6q1fljndax0rene8dhb/3440.OSC_cached.png?rlkey=33rydhcbt0drl9to51rlmizi3&st=0qwx82bm&dl=0"
width="1052" height="683"></p>
<p><br>
</p>
<p>Next image is the amount of cached memory used by each OSC, on
the compute node, for the second file.</p>
<p><br>
</p>
<p><img moz-do-not-send="false"
src="cid:part3.H7nHMg0v.B5R1WWuj@iodoctors.com"
alt="https://www.dropbox.com/scl/fi/xnmeoi0oni4x7zyy7ezfj/3440.B.OSC_cached.png?rlkey=557c55qdj60woelbyb3hf250b&st=x49bosvd&dl=0"
width="1052" height="683"></p>
<p><br>
</p>
<p>The following 3 plots are the same as for above, but are from the
second run of this job. This time I am doing a stat() of the
first file every 10 seconds, from a login node while the job is
running.</p>
<p><br>
</p>
<p><img moz-do-not-send="false"
src="cid:part4.sspJXTqE.FsdstK0f@iodoctors.com"
alt="https://www.dropbox.com/scl/fi/v63gm040hn1ljwzx70u2h/3442.fpa.png?rlkey=bbr7ltxfemdqsq5jt04967t99&st=74e9aqts&dl=0"
width="1052" height="683"></p>
<p><br>
</p>
<p><img moz-do-not-send="false"
src="cid:part5.nFk6a504.YMgdyQuO@iodoctors.com"
alt="https://www.dropbox.com/scl/fi/m80b3o2og8fy527ayizff/3442.OSC_cached.png?rlkey=b9wcrx86dpl7qolalu77q8yey&st=748an788&dl=0"
width="1052" height="683"></p>
<p><br>
</p>
<p><img moz-do-not-send="false"
src="cid:part6.0q0ChE2h.GZXiDbCp@iodoctors.com"
alt="https://www.dropbox.com/scl/fi/lxr5ya7ihk7kx6ez182xl/3442.B.OSC_cached.png?rlkey=5utkp5gdywocafvt8ohh5fpc4&st=7yhkai9i&dl=0"
width="1052" height="683"></p>
<p><br>
</p>
<div class="moz-cite-prefix">On 3/24/2026 10:40 AM, Patrick Farrell
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:DM6PR19MB2636CEB3053373505F59D5BAC948A@DM6PR19MB2636.namprd19.prod.outlook.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<style type="text/css" style="display:none;">P {margin-top:0;margin-bottom:0;}</style>
<div class="elementToProof"
style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Not as far as I know - can you be more specific about the
behavior change?</div>
<hr style="display:inline-block;width:98%" tabindex="-1">
<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif"
style="font-size:11pt" color="#000000"><b>From:</b>
lustre-discuss <a class="moz-txt-link-rfc2396E" href="mailto:lustre-discuss-bounces@lists.lustre.org"><lustre-discuss-bounces@lists.lustre.org></a>
on behalf of John Bauer via lustre-discuss
<a class="moz-txt-link-rfc2396E" href="mailto:lustre-discuss@lists.lustre.org"><lustre-discuss@lists.lustre.org></a><br>
<b>Sent:</b> Tuesday, March 24, 2026 10:35 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:lustre-discuss@lists.lustre.org">lustre-discuss@lists.lustre.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:lustre-discuss@lists.lustre.org"><lustre-discuss@lists.lustre.org></a><br>
<b>Subject:</b> [lustre-discuss] Lustre caching behavior</font>
<div> </div>
</div>
<div>
<p>All,</p>
<p>Is it a known effect that a stat() of a file on a given node
will change the caching behavior on a second node. I have
noticed that the caching behavior of Lustre on a dedicated
compute node will change significantly if I do intermittent
stats of the file of interest from the front-end node.</p>
<p>Thanks,</p>
<p>John</p>
</div>
</blockquote>
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