<html><body><p><font size="2">Joey,</font><br><br><font size="2">The </font><b><font size="2">subblocks-per-full-block</font></b><font size="2"> value cannot be specified when the file system is created, but is rather computed automatically by GPFS. In file systems with format older than 5.0, the value is fixed at 32. For file systems with format 5.0.0 or later, the value is computed based on the block size. See manpage for </font><b><font size="2">mmcrfs</font></b><font size="2">, in table where the </font><b><font size="2">-B BlockSize</font></b><font size="2"> option is explained. (Table 1. Block sizes and subblock sizes) . Say, for the default (in 5.0+) 4MB block size, the subblock size is 8KB.</font><br><br><font size="2">The minimum "practical" subblock size is 4KB, to keep 4KB-alignment to accommodate 4KN devices.</font><br><br><font size="2"> Felipe</font><br><br><font size="2">----<br>Felipe Knop knop@us.ibm.com<br>GPFS Development and Security<br>IBM Systems<br>IBM Building 008<br>2455 South Rd, Poughkeepsie, NY 12601<br>(845) 433-9314 T/L 293-9314<br><br></font><br><br><img width="16" height="16" src="cid:1__=8FBB082BDF8082F38f9e8a93df938690918c8FB@" border="0" alt="Inactive hide details for Joseph Mendoza ---06/25/2018 08:59:10 PM---Quick question, anyone know why GPFS wouldn't respect the "><font size="2" color="#424282">Joseph Mendoza ---06/25/2018 08:59:10 PM---Quick question, anyone know why GPFS wouldn't respect the default for the subblocks-per-full-block p</font><br><br><font size="2" color="#5F5F5F">From: </font><font size="2">Joseph Mendoza <jam@ucar.edu></font><br><font size="2" color="#5F5F5F">To: </font><font size="2">gpfsug main discussion list <gpfsug-discuss@spectrumscale.org></font><br><font size="2" color="#5F5F5F">Date: </font><font size="2">06/25/2018 08:59 PM</font><br><font size="2" color="#5F5F5F">Subject: </font><font size="2">[gpfsug-discuss] subblock sanity check in 5.0</font><br><font size="2" color="#5F5F5F">Sent by: </font><font size="2">gpfsug-discuss-bounces@spectrumscale.org</font><br><hr width="100%" size="2" align="left" noshade style="color:#8091A5; "><br><br><br><tt><font size="2">Quick question, anyone know why GPFS wouldn't respect the default for<br>the subblocks-per-full-block parameter when creating a new filesystem? <br>I'd expect it to be set to 512 for an 8MB block size but my guess is<br>that also specifying a metadata-block-size is interfering with it (by<br>being too small). This was a parameter recommended by the vendor for a<br>4.2 installation with metadata on dedicated SSDs in the system pool, any<br>best practices for 5.0? I'm guessing I'd have to bump it up to at least<br>4MB to get 512 subblocks for both pools.<br><br>fs1 created with:<br># mmcrfs fs1 -F fs1_ALL -A no -B 8M -i 4096 -m 2 -M 2 -r 1 -R 2 -j<br>cluster -n 9000 --metadata-block-size 512K --perfileset-quota<br>--filesetdf -S relatime -Q yes --inode-limit 20000000:10000000 -T /gpfs/fs1<br><br># mmlsfs fs1<br><snipped><br><br>flag value description<br>------------------- ------------------------<br>-----------------------------------<br> -f 8192 Minimum fragment (subblock)<br>size in bytes (system pool)<br> 131072 Minimum fragment (subblock)<br>size in bytes (other pools)<br> -i 4096 Inode size in bytes<br> -I 32768 Indirect block size in bytes<br><br> -B 524288 Block size (system pool)<br> 8388608 Block size (other pools)<br><br> -V 19.01 (5.0.1.0) File system version<br><br> --subblocks-per-full-block 64 Number of subblocks per<br>full block<br> -P system;DATA Disk storage pools in file<br>system<br><br><br>Thanks!<br>--Joey Mendoza<br>NCAR<br>_______________________________________________<br>gpfsug-discuss mailing list<br>gpfsug-discuss at spectrumscale.org<br></font></tt><tt><font size="2"><a href="http://gpfsug.org/mailman/listinfo/gpfsug-discuss">http://gpfsug.org/mailman/listinfo/gpfsug-discuss</a></font></tt><tt><font size="2"><br><br></font></tt><br><br><BR>
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