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--></style></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>I know this will be very confusing, but the code works different than one would think (not sure this is documented anywhere). The number of subblocks across pools of a fileystsem is calculated based on the smallest pools blocksize. <o:p></o:p></p><p class=MsoNormal>So given you have a 1MB blocksize in the system pool you will end up with 128 subblocks, now you have a 2<sup>nd</sup> pool (data) which will inherit the 128 subblocks and the code calculates a subblock size of 128k (16M/128=128k). <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Sven<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='margin-left:.5in'><b><span style='font-size:12.0pt;color:black'>From: </span></b><span style='font-size:12.0pt;color:black'><gpfsug-discuss-bounces@spectrumscale.org> on behalf of "Caubet Serrabou Marc (PSI)" <marc.caubet@psi.ch><br><b>Reply-To: </b>gpfsug main discussion list <gpfsug-discuss@spectrumscale.org><br><b>Date: </b>Tuesday, March 26, 2019 at 8:46 AM<br><b>To: </b>gpfsug main discussion list <gpfsug-discuss@spectrumscale.org><br><b>Subject: </b>[gpfsug-discuss] GPFS v5: Blocksizes and subblocks<o:p></o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p></div><div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>Hi all,<o:p></o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:0in;margin-bottom:12.0pt;margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'><o:p> </o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>Marc <o:p></o:p></span></p><div><div><div><div><p class=MsoNormal style='margin-left:.5in'><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></div><div><p class=MsoNormal style='margin-left:.5in'><span style='font-size:10.0pt;font-family:"Tahoma",sans-serif;color:black'>Forschungsstrasse, 111<o:p></o:p></span></p></div><div><p class=MsoNormal style='margin-left:.5in'><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: marc.caubet@psi.ch<o:p></o:p></span></p></div></div></div></div></div></div><p class=MsoNormal style='margin-left:.5in'>_______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss <o:p></o:p></p></div></body></html>