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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">you have two storage pools. The calculation of the number of subblocks is performed on the system pool with 1MiB blocksize
</span><span style="font-size:11.0pt;font-family:Wingdings;color:#1F497D">à</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> subblock size of 8kiB
</span><span style="font-size:11.0pt;font-family:Wingdings;color:#1F497D">à</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> 128 subblocks. The other pool inherits the “128 subblocks”, as all pools in a filesystem will have
the same number of subblocks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="DE" style="font-size:10.5pt;font-family:"Courier New";color:#1F497D">Mit freundlichen Grüssen / Best regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="DE" style="font-size:10.5pt;font-family:"Courier New";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Courier New";color:#1F497D">Michael Hennecke<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.5pt;font-family:"Courier New";color:#1F497D">HPC Chief Technologist - HPC and AI Business Unit
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Courier New";color:#1F497D">--<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Courier New";color:#1F497D">Lenovo
</span><span lang="DE" style="font-size:8.0pt;font-family:"Courier New";color:#1F497D">Global Technology (Germany) GmbH * Am Zehnthof 77 * D-45307 Essen * Germany
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="DE" style="font-size:8.0pt;font-family:"Courier New";color:#1F497D">Geschäftsführung: Colm Gleeson, Christophe Laurent * Sitz der Gesellschaft: Stuttgart * HRB-Nr.: 758298, AG Stuttgart</span><span lang="DE" style="font-size:11.0pt;font-family:"Courier New";color:#1F497D"><o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="DE" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> gpfsug-discuss-bounces@spectrumscale.org <gpfsug-discuss-bounces@spectrumscale.org>
<b>On Behalf Of </b>Caubet Serrabou Marc (PSI)<br>
<b>Sent:</b> Tuesday, 26 March, 2019 16:40<br>
<b>To:</b> gpfsug main discussion list <gpfsug-discuss@spectrumscale.org><br>
<b>Subject:</b> [External] [gpfsug-discuss] GPFS v5: Blocksizes and subblocks<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">Hi all,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">according to several GPFS presentations as well as according to the man pages:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> Table 1. Block sizes and subblock sizes<br>
<br>
+-------------------------------+-------------------------------+<br>
| Block size | Subblock size |<br>
+-------------------------------+-------------------------------+<br>
| 64 KiB | 2 KiB |<br>
+-------------------------------+-------------------------------+<br>
| 128 KiB | 4 KiB |<br>
+-------------------------------+-------------------------------+<br>
| 256 KiB, 512 KiB, 1 MiB, 2 | 8 KiB |<br>
| MiB, 4 MiB | |<br>
+-------------------------------+-------------------------------+<br>
| 8 MiB, 16 MiB | 16 KiB |<br>
+-------------------------------+-------------------------------+</span><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">A block size of 8MiB or 16MiB should contain subblocks of 16KiB.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">However, when creating a new filesystem with 16MiB blocksize, looks like is using 128KiB subblocks:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">[root@merlindssio01 ~]# mmlsfs merlin<br>
flag value description<br>
------------------- ------------------------ -----------------------------------<br>
-f 8192 Minimum fragment (subblock) size in bytes (system pool)<br>
131072 Minimum fragment (subblock) size in bytes (other pools)<br>
-i 4096 Inode size in bytes<br>
-I 32768 Indirect block size in bytes<br>
.</span><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">.</span><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">.</span><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> -n 128 Estimated number of nodes that will mount file system<br>
-B 1048576 Block size (system pool)<br>
16777216 Block size (other pools)<br>
.</span><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">.</span><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New";color:black">.</span><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">What am I missing? According to documentation, I expect this to be a fixed value, or it isn't at all?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">On the other hand, I don't really understand the concept 'Indirect block size in bytes', can somebody clarify or provide some details about this setting?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">Thanks a lot and best regards,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">Marc
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">_________________________________________<br>
Paul Scherrer Institut <br>
High Performance Computing<br>
Marc Caubet Serrabou<br>
Building/Room: WHGA/019A<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">Forschungsstrasse, 111<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black">5232 Villigen PSI<br>
Switzerland<br>
<br>
Telephone: +41 56 310 46 67<br>
E-Mail: <a href="mailto:marc.caubet@psi.ch">marc.caubet@psi.ch</a><o:p></o:p></span></p>
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