<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<style type="text/css">BODY {
FONT-FAMILY: arial
}
</style>
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
@font-face
{font-family:"Lucida Console";
panose-1:2 11 6 9 4 5 4 2 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Vorformatiert Zchn";
margin:0cm;
font-size:10.0pt;
font-family:"Courier New";}
span.HTMLVorformatiertZchn
{mso-style-name:"HTML Vorformatiert Zchn";
mso-style-priority:99;
mso-style-link:"HTML Vorformatiert";
font-family:Consolas;}
span.pfptpreheader1
{mso-style-name:pfptpreheader1;
display:none;}
span.pfpttitlemso1
{mso-style-name:pfpttitlemso1;
font-family:"Arial",sans-serif;
color:black;
font-weight:bold;}
span.pfptsubtitlemso1
{mso-style-name:pfptsubtitlemso1;
font-family:"Arial",sans-serif;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 2.0cm 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="DE" link="blue" vlink="purple" style="word-wrap:break-word">
<p></p>
<div class="WordSection1">
<p class="MsoNormal"><span lang="EN-US" style="font-size:12.0pt;font-family:"Arial",sans-serif;mso-fareast-language:EN-US">Hallo Uwe,<br>
are numactl already installed on that affected node? If it missed the numa scale stuff is not working.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div></div>
</div>
<p></p>
<p><font style="font-family:Arial;">Renar</font> <font style="font-family:Arial;">Grunenberg</font><br>
<font style="font-family:Arial;">Abteilung Informatik - Betrieb</font><br>
<br>
<font style="font-family:Arial;">HUK-COBURG</font><br>
<font style="font-family:Arial;">Bahnhofsplatz</font><br>
<font style="font-family:Arial;">96444</font> <font style="font-family:Arial;">Coburg</font><br>
<table class="220e457a-7cdf-4856-91a8-c30341e9403eTable" style="font-family:Arial;">
<tbody>
<tr>
<td><font style="font-family:Arial;"><font style="font-family:Arial;"><font style="font-family:Arial;">Telefon:</font></font></font></td>
<td><font style="font-family:Arial;"><font style="font-family:Arial;"><font style="font-family:Arial;">09561 96-44110</font></font></font></td>
</tr>
<tr>
<td><font style="font-family:Arial;"><font style="font-family:Arial;"><font style="font-family:Arial;">Telefax:</font></font></font></td>
<td><font style="font-family:Arial;"><font style="font-family:Arial;"><font style="font-family:Arial;">09561 96-44104</font></font></font></td>
</tr>
<tr>
<td><font style="font-family:Arial;"><font style="font-family:Arial;"><font style="font-family:Arial;">E-Mail:</font></font></font></td>
<td><font style="font-family:Arial;"><font style="font-family:Arial;">Renar.Grunenberg@huk-coburg.de</font></font></td>
</tr>
<tr>
<td><font style="font-family:Arial;"><font style="font-family:Arial;"><font style="font-family:Arial;">Internet:</font></font></font></td>
<td><font style="font-family:Arial;"><font style="font-family:Arial;"><font style="font-family:Arial;">www.huk.de</font></font></font></td>
</tr>
</tbody>
</table>
</p>
<hr id="HR1">
<font face="Arial"><font size="1">HUK-COBURG Haftpflicht-Unterstützungs-Kasse kraftfahrender Beamter Deutschlands a. G. in Coburg<br>
Reg.-Gericht Coburg HRB 100; St.-Nr. 9212/101/00021<br>
Sitz der Gesellschaft: Bahnhofsplatz, 96444 Coburg<br>
Vorsitzender des Aufsichtsrats: Prof. Dr. Heinrich R. Schradin.<br>
Vorstand: Klaus-Jürgen Heitmann (Sprecher), Stefan Gronbach, Dr. Hans Olav Herøy, Dr. Helen Reck, Dr. Jörg Rheinländer, Thomas Sehn, Daniel Thomas.<br>
</font>
<hr id="HR1">
</font><font size="1" face="Arial">Diese Nachricht enthält vertrauliche und/oder rechtlich geschützte Informationen.<br>
Wenn Sie nicht der richtige Adressat sind oder diese Nachricht irrtümlich erhalten haben,<br>
informieren Sie bitte sofort den Absender und vernichten Sie diese Nachricht.<br>
Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser Nachricht ist nicht gestattet.<br>
<br>
This information may contain confidential and/or privileged information.<br>
If you are not the intended recipient (or have received this information in error) please notify the<br>
sender immediately and destroy this information.<br>
Any unauthorized copying, disclosure or distribution of the material in this information is strictly forbidden.<br>
</font>
<hr id="HR1">
<p></p>
<p></p>
<p></p>
<div class="WordSection1">
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b>Von:</b> gpfsug-discuss-bounces@spectrumscale.org <gpfsug-discuss-bounces@spectrumscale.org>
<b>Im Auftrag von </b>Uwe Falke<br>
<b>Gesendet:</b> Montag, 28. Februar 2022 10:17<br>
<b>An:</b> gpfsug-discuss@spectrumscale.org<br>
<b>Betreff:</b> Re: [gpfsug-discuss] IO sizes<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p>Hi, Kumaran, <o:p></o:p></p>
<p>that would explain the smaller IOs before the reboot, but not the larger-than-4MiB IOs afterwards on that machine.<o:p></o:p></p>
<p>Then, I already saw that the numaMemoryInterleave setting seems to have no effect (on that very installation), I just have not yet requested a PMR for it. I'd checked memory usage of course and saw that regardless of this setting always one socket's memory
is almost completely consumed while the other one's is rather empty - looks like a bug to me, but that needs further investigation.<o:p></o:p></p>
<p>Uwe<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">On 24.02.22 15:32, Kumaran Rajaram wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Hi Uwe,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">>> But what puzzles me even more: one of the server compiles IOs even smaller, varying between 3.2MiB and 3.6MiB mostly - both for reads and writes ... I just cannot see why.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">IMHO, If GPFS on this particular NSD server was restarted often during the setup, then it is possible that the GPFS pagepool may not be contiguous. As a result, GPFS 8MiB buffer in the pagepool might be a scatter-gather (SG) list with many
small entries (in the memory) resulting in smaller I/O when these buffers are issued to the disks. The fix would be to reboot the server and start GPFS so that pagepool is contiguous resulting in 8MiB buffer to be comprised of 1 (or fewer) SG entries.
<o:p></o:p></p>
<p>>>In the current situation (i.e. with IOs bit larger than 4MiB) setting max_sectors_kB to 4096 might do the trick, but as I do not know the cause for that behaviour it might well start to issue IOs >>smaller than 4MiB again at some point, so that is not
a nice solution.<o:p></o:p></p>
<p class="MsoNormal">It will be advised not to restart GPFS often in the NSD servers (in production) to keep the pagepool contiguous. Ensure that there is enough free memory in NSD server and not run any memory intensive jobs so that pagepool is not impacted
(e.g. swapped out). <o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Also, enable GPFS numaMemoryInterleave=yes and verify that pagepool is equally distributed across the NUMA domains for good performance. GPFS numaMemoryInterleave=yes requires that numactl packages are installed and then GPFS restarted.<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Lucida Console",serif"> </span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif"># mmfsadm dump config | egrep "numaMemory|pagepool "</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">! numaMemoryInterleave yes</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">! pagepool 282394099712</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Lucida Console",serif"> </span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif"># pgrep mmfsd | xargs numastat -p</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif"> </span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">Per-node process memory usage (in MBs) for PID 2120821 (mmfsd)</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif"> Node 0 Node 1 Total</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif"> --------------- --------------- ---------------</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">Huge 0.00 0.00 0.00</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">Heap 1.26 3.26 4.52</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">Stack 0.01 0.01 0.02</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">Private 137710.43 137709.96 275420.39</span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">---------------- --------------- --------------- ---------------</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Lucida Console",serif">Total 137711.70 137713.23 275424.92</span><o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">My two cents,<o:p></o:p></p>
<p class="MsoNormal">-Kums<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<p class="MsoNormal">Kumaran Rajaram<o:p></o:p></p>
<p class="MsoNormal"><img width="135" height="48" style="width:1.4062in;height:.5in" id="Picture_x0020_1" src="cid:image001.png@01D82CA6.6F82DC70"><o:p></o:p></p>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b>From:</b> <a href="mailto:gpfsug-discuss-bounces@spectrumscale.org">
gpfsug-discuss-bounces@spectrumscale.org</a> <a href="mailto:gpfsug-discuss-bounces@spectrumscale.org">
<gpfsug-discuss-bounces@spectrumscale.org></a> <b>On Behalf Of </b>Uwe Falke<br>
<b>Sent:</b> Wednesday, February 23, 2022 8:04 PM<br>
<b>To:</b> <a href="mailto:gpfsug-discuss@spectrumscale.org">gpfsug-discuss@spectrumscale.org</a><br>
<b>Subject:</b> Re: [gpfsug-discuss] IO sizes<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<p>Hi, <o:p></o:p></p>
<p>the test bench is gpfsperf running on up to 12 clients with 1...64 threads doing sequential reads and writes , file size per gpfsperf process is 12TB (with 6TB I saw caching effects in particular for large thread numbers ...)
<o:p></o:p></p>
<p>As I wrote initially: GPFS is issuing nothing but 8MiB IOs to the data disks, as expected in that case.
<o:p></o:p></p>
<p>Interesting thing though: <o:p></o:p></p>
<p>I have rebooted the suspicious node. Now, it does not issue smaller IOs than the others, but -- unbelievable -- larger ones (up to about 4.7MiB). This is still harmful as also that size is incompatible with full stripe writes on the storage ( 8+2 disk groups,
i.e. logically RAID6)<o:p></o:p></p>
<p>Currently, I draw this information from the storage boxes; I have not yet checked iostat data for that benchmark test after the reboot (before, when IO sizes were smaller, we saw that both in iostat and in the perf data retrieved from the storage controllers).<o:p></o:p></p>
<p> <o:p></o:p></p>
<p>And: we have a separate data pool , hence dataOnly NSDs, I am just talking about these ...
<o:p></o:p></p>
<p> <o:p></o:p></p>
<p>As for "Are you sure that Linux OS is configured the same on all 4 NSD servers?." - of course there are not two boxes identical in the world. I have actually not installed those machines, and, yes, i also considered reinstalling them (or at least the disturbing
one).<o:p></o:p></p>
<p>However, I do not have reason to assume or expect a difference, the supplier has just implemented these systems recently from scratch.
<o:p></o:p></p>
<p> <o:p></o:p></p>
<p>In the current situation (i.e. with IOs bit larger than 4MiB) setting max_sectors_kB to 4096 might do the trick, but as I do not know the cause for that behaviour it might well start to issue IOs smaller than 4MiB again at some point, so that is not a nice
solution.<o:p></o:p></p>
<p> <o:p></o:p></p>
<p>Thanks<o:p></o:p></p>
<p>Uwe<o:p></o:p></p>
<p> <o:p></o:p></p>
<div>
<p class="MsoNormal">On 23.02.22 22:20, Andrew Beattie wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Alex, <o:p></o:p></p>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Metadata will be 4Kib <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Depending on the filesystem version you will also have subblocks to consider V4 filesystems have 1/32 subblocks, V5 filesystems have 1/1024 subblocks (assuming metadata and data block size is the same)<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><br>
My first question would be is “ Are you sure that Linux OS is configured the same on all 4 NSD servers?.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">My second question would be do you know what your average file size is if most of your files are smaller than your filesystem block size, then you are always going to be performing writes using groups of subblocks rather than a full block
writes.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Regards, <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Andrew<o:p></o:p></p>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><br>
<br>
<br>
<o:p></o:p></p>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal" style="margin-bottom:12.0pt">On 24 Feb 2022, at 04:39, Alex Chekholko
<a href="mailto:alex@calicolabs.com"><alex@calicolabs.com></a> wrote:<o:p></o:p></p>
</blockquote>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal"> <span class="pfptpreheader1"><span style="font-size:1.0pt;color:white">Hi, Metadata I/Os will always be smaller than the usual data block size, right? Which version of GPFS? Regards, Alex On Wed, Feb 23, 2022 at 10:26 AM Uwe Falke
<a href="mailto:uwe.falke@kit.edu"><uwe.falke@kit.edu></a> wrote: Dear all, sorry for asking a question which seems
</span></span><span style="font-size:1.0pt;color:white">ZjQcmQRYFpfptBannerStart</span>
<o:p></o:p></p>
<table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" width="100%" style="width:100.0%;border-radius:4px">
<tbody>
<tr>
<td style="padding:2.25pt 0cm 12.0pt 0cm">
<table class="MsoNormalTable" border="1" cellspacing="0" cellpadding="0" width="100%" style="width:100.0%;background:#D0D8DC;border:none;border-top:solid #90A4AE 3.0pt">
<tbody>
<tr>
<td valign="top" style="border:none;padding:0cm 7.5pt 3.75pt 4.5pt">
<table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" align="left">
<tbody>
<tr>
<td style="padding:3.0pt 6.0pt 3.0pt 6.0pt">
<p class="MsoNormal"><span class="pfpttitlemso1"><span style="font-size:10.5pt">This Message Is From an External Sender
</span></span><o:p></o:p></p>
</td>
</tr>
<tr>
<td style="padding:3.0pt 6.0pt 3.0pt 6.0pt">
<p class="MsoNormal"><span class="pfptsubtitlemso1"><span style="font-size:9.0pt;color:black">This message came from outside your organization.
</span></span><o:p></o:p></p>
</td>
</tr>
</tbody>
</table>
</td>
</tr>
</tbody>
</table>
</td>
</tr>
</tbody>
</table>
<p class="MsoNormal"><span style="font-size:1.0pt;color:white">ZjQcmQRYFpfptBannerEnd<br>
<br>
<br>
</span><o:p></o:p></p>
<div>
<p class="MsoNormal">Hi, <o:p></o:p></p>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Metadata I/Os will always be smaller than the usual data block size, right?<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Which version of GPFS?<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Regards,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Alex<o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<div>
<p class="MsoNormal">On Wed, Feb 23, 2022 at 10:26 AM Uwe Falke <<a href="mailto:uwe.falke@kit.edu">uwe.falke@kit.edu</a>> wrote:<o:p></o:p></p>
</div>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt">
<p class="MsoNormal">Dear all,<br>
<br>
sorry for asking a question which seems not directly GPFS related:<br>
<br>
In a setup with 4 NSD servers (old-style, with storage controllers in <br>
the back end), 12 clients and 10 Seagate storage systems, I do see in <br>
benchmark tests that just one of the NSD servers does send smaller IO <br>
requests to the storage than the other 3 (that is, both reads and <br>
writes are smaller).<br>
<br>
The NSD servers form 2 pairs, each pair is connected to 5 seagate boxes <br>
( one server to the controllers A, the other one to controllers B of the <br>
Seagates, resp.).<br>
<br>
All 4 NSD servers are set up similarly:<br>
<br>
kernel: 3.10.0-1160.el7.x86_64 #1 SMP<br>
<br>
HBA: Broadcom / LSI Fusion-MPT 12GSAS/PCIe Secure SAS38xx<br>
<br>
driver : mpt3sas 31.100.01.00<br>
<br>
max_sectors_kb=8192 (max_hw_sectors_kb=16383 , not 16384, as limited by <br>
mpt3sas) for all sd devices and all multipath (dm) devices built on top.<br>
<br>
scheduler: deadline<br>
<br>
multipath (actually we do have 3 paths to each volume, so there is some <br>
asymmetry, but that should not affect the IOs, shouldn't it?, and if it <br>
did we would see the same effect in both pairs of NSD servers, but we do <br>
not).<br>
<br>
All 4 storage systems are also configured the same way (2 disk groups / <br>
pools / declustered arrays, one managed by ctrl A, one by ctrl B, and <br>
8 volumes out of each; makes altogether 2 x 8 x 10 = 160 NSDs).<br>
<br>
<br>
GPFS BS is 8MiB , according to iohistory (mmdiag) we do see clean IO <br>
requests of 16384 disk blocks (i.e. 8192kiB) from GPFS.<br>
<br>
The first question I have - but that is not my main one: I do see, both <br>
in iostat and on the storage systems, that the default IO requests are <br>
about 4MiB, not 8MiB as I'd expect from above settings (max_sectors_kb <br>
is really in terms of kiB, not sectors, cf. <br>
<a href="https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.kernel.org%2Fdoc%2FDocumentation%2Fblock%2Fqueue-sysfs.txt&data=04%7C01%7Ckrajaram%40geocomputing.net%7C52cc6360e6ea4be737ba08d9f7317d78%7C229a2792a5064f25b3bdbab585cec3ed%7C0%7C0%7C637812615096678246%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=II8k%2FHzrU7BC%2FVejg9AujgZGk1E0XTz8QCpH6IE6RGM%3D&reserved=0" target="_blank">https://www.kernel.org/doc/Documentation/block/queue-sysfs.txt</a>).<br>
<br>
But what puzzles me even more: one of the server compiles IOs even <br>
smaller, varying between 3.2MiB and 3.6MiB mostly - both for reads and <br>
writes ... I just cannot see why.<br>
<br>
I have to suspect that this will (in writing to the storage) cause <br>
incomplete stripe writes on our erasure-coded volumes (8+2p)(as long as <br>
the controller is not able to re-coalesce the data properly; and it <br>
seems it cannot do it completely at least)<br>
<br>
<br>
If someone of you has seen that already and/or knows a potential <br>
explanation I'd be glad to learn about.<br>
<br>
<br>
And if some of you wonder: yes, I (was) moved away from IBM and am now <br>
at KIT.<br>
<br>
Many thanks in advance<br>
<br>
Uwe<br>
<br>
<br>
-- <br>
Karlsruhe Institute of Technology (KIT)<br>
Steinbuch Centre for Computing (SCC)<br>
Scientific Data Management (SDM)<br>
<br>
Uwe Falke<br>
<br>
Hermann-von-Helmholtz-Platz 1, Building 442, Room 187<br>
D-76344 Eggenstein-Leopoldshafen<br>
<br>
Tel: +49 721 608 28024<br>
Email: <a href="mailto:uwe.falke@kit.edu" target="_blank">uwe.falke@kit.edu</a><br>
<a href="https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.scc.kit.edu%2F&data=04%7C01%7Ckrajaram%40geocomputing.net%7C52cc6360e6ea4be737ba08d9f7317d78%7C229a2792a5064f25b3bdbab585cec3ed%7C0%7C0%7C637812615096678246%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=mXwzkLB1EFB1Dh31rVRMwJZBY4CBbHcJduc9gK6M71A%3D&reserved=0" target="_blank">www.scc.kit.edu</a><br>
<br>
Registered office:<br>
Kaiserstraße 12, 76131 Karlsruhe, Germany<br>
<br>
KIT – The Research University in the Helmholtz Association<br>
<br>
_______________________________________________<br>
gpfsug-discuss mailing list<br>
gpfsug-discuss at <a href="https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fspectrumscale.org%2F&data=04%7C01%7Ckrajaram%40geocomputing.net%7C52cc6360e6ea4be737ba08d9f7317d78%7C229a2792a5064f25b3bdbab585cec3ed%7C0%7C0%7C637812615096678246%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=G6bjUWlzkKzR2ptGcLffwD8qF2IT9vkruoevFoTwNE0%3D&reserved=0" target="_blank">
spectrumscale.org</a><br>
<a href="https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgpfsug.org%2Fmailman%2Flistinfo%2Fgpfsug-discuss&data=04%7C01%7Ckrajaram%40geocomputing.net%7C52cc6360e6ea4be737ba08d9f7317d78%7C229a2792a5064f25b3bdbab585cec3ed%7C0%7C0%7C637812615096678246%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=G9l4PMuzdNA%2BwtAtWK%2BApoXxvKn5jZKeP%2FENOVc9xXg%3D&reserved=0" target="_blank">http://gpfsug.org/mailman/listinfo/gpfsug-discuss</a><o:p></o:p></p>
</blockquote>
</div>
</div>
</blockquote>
</div>
<p class="MsoNormal"><br>
<br>
<br>
<br>
<br>
<o:p></o:p></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>gpfsug-discuss mailing list<o:p></o:p></pre>
<pre>gpfsug-discuss at spectrumscale.org<o:p></o:p></pre>
<pre><a href="https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgpfsug.org%2Fmailman%2Flistinfo%2Fgpfsug-discuss&data=04%7C01%7Ckrajaram%40geocomputing.net%7C52cc6360e6ea4be737ba08d9f7317d78%7C229a2792a5064f25b3bdbab585cec3ed%7C0%7C0%7C637812615096678246%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=G9l4PMuzdNA%2BwtAtWK%2BApoXxvKn5jZKeP%2FENOVc9xXg%3D&reserved=0">http://gpfsug.org/mailman/listinfo/gpfsug-discuss</a><o:p></o:p></pre>
</blockquote>
<pre>-- <o:p></o:p></pre>
<pre>Karlsruhe Institute of Technology (KIT)<o:p></o:p></pre>
<pre>Steinbuch Centre for Computing (SCC)<o:p></o:p></pre>
<pre>Scientific Data Management (SDM)<o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<pre>Uwe Falke<o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<pre>Hermann-von-Helmholtz-Platz 1, Building 442, Room 187<o:p></o:p></pre>
<pre>D-76344 Eggenstein-Leopoldshafen<o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<pre>Tel: +49 721 608 28024<o:p></o:p></pre>
<pre>Email: <a href="mailto:uwe.falke@kit.edu">uwe.falke@kit.edu</a><o:p></o:p></pre>
<pre><a href="https://nam02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.scc.kit.edu%2F&data=04%7C01%7Ckrajaram%40geocomputing.net%7C52cc6360e6ea4be737ba08d9f7317d78%7C229a2792a5064f25b3bdbab585cec3ed%7C0%7C0%7C637812615096678246%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=mXwzkLB1EFB1Dh31rVRMwJZBY4CBbHcJduc9gK6M71A%3D&reserved=0">www.scc.kit.edu</a><o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<pre>Registered office:<o:p></o:p></pre>
<pre>Kaiserstraße 12, 76131 Karlsruhe, Germany<o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<pre>KIT – The Research University in the Helmholtz Association <o:p></o:p></pre>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif"><br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>gpfsug-discuss mailing list<o:p></o:p></pre>
<pre>gpfsug-discuss at spectrumscale.org<o:p></o:p></pre>
<pre><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss">http://gpfsug.org/mailman/listinfo/gpfsug-discuss</a><o:p></o:p></pre>
</blockquote>
<pre>-- <o:p></o:p></pre>
<pre>Karlsruhe Institute of Technology (KIT)<o:p></o:p></pre>
<pre>Steinbuch Centre for Computing (SCC)<o:p></o:p></pre>
<pre>Scientific Data Management (SDM)<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Uwe Falke<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Hermann-von-Helmholtz-Platz 1, Building 442, Room 187<o:p></o:p></pre>
<pre>D-76344 Eggenstein-Leopoldshafen<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Tel: +49 721 608 28024<o:p></o:p></pre>
<pre>Email: <a href="mailto:uwe.falke@kit.edu">uwe.falke@kit.edu</a><o:p></o:p></pre>
<pre><a href="http://www.scc.kit.edu">www.scc.kit.edu</a><o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>Registered office:<o:p></o:p></pre>
<pre>Kaiserstraße 12, 76131 Karlsruhe, Germany<o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre>KIT – The Research University in the Helmholtz Association <o:p></o:p></pre>
</div>
<p></p>
<p></p>
<p></p>
<p></p>
<p></p>
<p></p>
<p></p>
<p></p>
<p></p>
<p></p>
<p></p>
</body>
</html>