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<p class="MsoNormal">><span style="font-size:12.0pt;color:black">></span><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">[2]
<i>[...] I believe I'm correct in saying that inodes are not the only things to live on the metadata pool, so I assume that some other metadata might benefit from the larger block/subblock size. But looking at the number of inodes, the inode size, and the
space consumed in the system pool, it really looks like the majority of space consumed is by inodes.[...]
</i></span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></span></p>
<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">>you may need to consider snapshots and directories , which all contributes to MD space </span></span><span style="font-size:12.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">>predicting the space requirements for MD for directories is always hard, because the size of a directory is depending on the file's name length, the
users will create... </span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Unless you enable encryption. In which case NO metadata will be stored on MD disks/devices.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Ed Wahl<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Ohio Supercomputer Center<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b>From:</b> gpfsug-discuss <gpfsug-discuss-bounces@gpfsug.org>
<b>On Behalf Of </b>Olaf Weiser<br>
<b>Sent:</b> Wednesday, August 2, 2023 7:43 AM<br>
<b>To:</b> gpfsug-discuss@gpfsug.org<br>
<b>Subject:</b> Re: [gpfsug-discuss] Inode size, and system pool subblock<o:p></o:p></p>
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<p class="MsoNormal" style="mso-line-height-alt:.75pt"><span style="font-size:1.0pt;color:white">Hallo Peter, [1] [. . . ] having a smaller inode size than the subblock size means there's a big wastage on disk usage, with no performance benefit to doing so[. . . ]
in short - yes </span><span style="font-size:1.0pt;font-family:"Segoe UI Emoji",sans-serif;color:white">😉</span><span style="font-size:1.0pt;color:white"> [2] [. . . ] I believe I'm correct in saying that inodes are not
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Hallo Peter, <o:p>
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<p class="MsoNormal"><span class="xcontentpasted0"><span style="font-family:"Arial",sans-serif;color:black;background:white">[1]
<i>[...] having a smaller inode size than the subblock size means</i></span></span><span class="contentpasted0"><i><span style="font-family:"Arial",sans-serif;color:black"> there's a big wastage on disk usage, with no performance benefit to doing so[...]
</span></i></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">in short - yes
</span></span><span class="contentpasted0"><span style="font-family:"Segoe UI Emoji",sans-serif;color:black">😉</span></span><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">
</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">[2]
<i>[...] I believe I'm correct in saying that inodes are not the only things to live on the metadata pool, so I assume that some other metadata might benefit from the larger block/subblock size. But looking at the number of inodes, the inode size, and the
space consumed in the system pool, it really looks like the majority of space consumed is by inodes.[...]
</i></span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">you may need to consider snapshots and directories , which all contributes to MD space</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black"> </span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">predicting the space requirements for MD for directories is always hard, because the size of a directory is depending on the file's name length, the
users will create... </span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">further more, using a less than 4k inode size makes also not much sense, when taking into account, that NVMEs and other modern block storage devices
comes with a hardware block size of 4k (even though GPFS still can deal with 512 Bytes per sector)
</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-family:"Arial",sans-serif;color:black">hope this helps ..
</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="color:black">Von:</span></b><span style="color:black"> gpfsug-discuss <</span><a href="mailto:gpfsug-discuss-bounces@gpfsug.org">gpfsug-discuss-bounces@gpfsug.org</a><span style="color:black">> im Auftrag von Peter Chase
<</span><a href="mailto:peter.chase@metoffice.gov.uk">peter.chase@metoffice.gov.uk</a><span style="color:black">><br>
<b>Gesendet:</b> Mittwoch, 2. August 2023 11:09<br>
<b>An:</b> </span><a href="mailto:gpfsug-discuss@gpfsug.org">gpfsug-discuss@gpfsug.org</a><span style="color:black"> <</span><a href="mailto:gpfsug-discuss@gpfsug.org">gpfsug-discuss@gpfsug.org</a><span style="color:black">><br>
<b>Betreff:</b> [EXTERNAL] [gpfsug-discuss] Inode size, and system pool subblock</span>
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<p class="MsoNormal" style="mso-line-height-alt:.75pt"><span style="font-size:1.0pt;color:white">Good Morning, I have a question about inode size vs subblock size. Can anyone think of a reason that the chosen inode size of a scale filesystem should be smaller
than the subblock size for the metadata pool? I'm looking at an existing filesystem,
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Good Morning,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">I have a question about inode size vs subblock size. Can anyone think of a reason that the chosen inode size of a scale filesystem should be smaller than the subblock
size for the metadata pool?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">I'm looking at an existing filesystem, the inode size is 2KiB, and the subblock is 4KiB.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">It feels like I'm missing something. If I've understood the docs on blocks and subblocks correctly, it sounds like the subblock is the smallest atomic access size.
Meaning with a 4K subblock, and a 2K inode, reading the inode would return its contents and 2K of empty subblock every time. So, in my head (and maybe only there), <span class="xcontentpasted0"><span style="background:white">having a smaller inode size than
the subblock size means</span></span> there's a big wastage on disk usage, with no performance benefit to doing so.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">I believe I'm correct in saying that inodes are not the only things to live on the metadata pool, so I assume that some other metadata might benefit from the larger
block/subblock size. But looking at the number of inodes, the inode size, and the space consumed in the system pool, it really looks like the majority of space consumed is by inodes.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">As I said, I feel like I'm missing something, so if anyone can tell me where I'm wrong it would be greatly appreciated!<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Sincerely,<o:p></o:p></span></p>
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<p><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">Pete Chase</span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
<p><span style="font-size:10.0pt;font-family:"Arial",sans-serif;color:black">UKMO</span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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