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<div><br></div><div>Run a mmlsnsd -X I suspect you will see that GPFS is using one of the /dev/sd* "generic" paths to the LUN, not the /dev/mapper/ path. In our case the device is setup as dmm <br></div><div><br></div><div>[root@service5 ~]# mmlsnsd -X<br><br> Disk name NSD volume ID Device Devtype Node name Remarks <br>---------------------------------------------------------------------------------------------------<br> volume1 0972B6CD587CD8E0 /dev/dm-0 dmm service5.pok.stglabs.ibm.com server node<br> volume1 0972B6CD587CD8E0 /dev/dm-0 dmm service6.pok.stglabs.ibm.com server node<br> volume2 0972B6CE587CD8E4 /dev/dm-4 dmm service5.pok.stglabs.ibm.com server node<br> volume2 0972B6CE587CD8E4 /dev/dm-3 dmm service6.pok.stglabs.ibm.com server node<br> volume3 0972B6CD587CD8E7 /dev/dm-1 dmm service5.pok.stglabs.ibm.com server node<br> volume3 0972B6CD587CD8E7 /dev/dm-2 dmm service6.pok.stglabs.ibm.com server node<br> volume4 0972B6CE587CF625 /dev/dm-3 dmm service5.pok.stglabs.ibm.com server node<br> volume4 0972B6CE587CF625 /dev/dm-4 dmm service6.pok.stglabs.ibm.com server node<br><br>[root@service5 ~]# grep volume1 /var/mmfs/gen/mmsdrfs | grep SG_DISK<br>%%home%%:60_SG_DISKS:gpfs5:1:volume1:0:5001:dataAndMetadata:0972B6CD587CD8E0:nsd:service5.pok.stglabs.ibm.com,service6.pok.stglabs.ibm.com::other::dmm:user:::quorumDisk:ready::system:service5.pok.stglabs.ibm.com,service6.pok.stglabs.ibm.com:::::<br>[root@service5 ~]# <br><br><div><br></div><div>If you run an tspreparedisk -s it will show you all of the paths. </div><div><br></div><div>[root@service5 ~]# tspreparedisk -s | grep 0972B6CD587CD8E0<br>0972B6CD587CD8E0 /dev/sda generic <br>0972B6CD587CD8E0 /dev/sdk generic <br>0972B6CD587CD8E0 /dev/sdu generic <br>0972B6CD587CD8E0 /dev/sdah generic <br>0972B6CD587CD8E0 /dev/dm-0 dmm <br>[root@service5 ~]# <br><div><br></div><div>Jim<br></div><div><br></div><div><br></div></div></div><div><br></div><div>Jim<br></div>
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On Wednesday, January 17, 2018, 5:12:10 PM EST, Bryan Banister <bbanister@jumptrading.com> wrote:
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<p class="yiv9990787954MsoNormal">Hi all,</p>
<p class="yiv9990787954MsoNormal"> </p>
<p class="yiv9990787954MsoNormal">We are reviewing some of our configurations and were not sure what to make of the NSD Device Types that GPFS uses and what, if anything, do they change about how GPFS accesses/recovers/manages/etc the underlying storage based on this setting.</p>
<p class="yiv9990787954MsoNormal"> </p>
<p class="yiv9990787954MsoNormal">The documentation doesn’t say much about it other than to consult the /usr/lpp/mmfs/bin/mmdevdiscover command (no man page), which has this section:</p>
<p class="yiv9990787954MsoNormal"> </p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># Known disk types currently are:</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;">#</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># powerdisk - EMC power path disk</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># vpath - IBM virtual path disk</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># dmm - Device-Mapper Multipath (DMM)</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># dlmfdrv - Hitachi dlm</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># hdisk - AIX hard disk</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># lv - AIX logical volume. Historical usage only.</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># Not allowed as a new device to mmcrnsd.</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># gpt - GPFS partition on Windows disk</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># generic - Device having no unique failover or multipathing</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># characteristic (predominantly Linux devices).</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"># dasd - DASD device (for Linux on z Systems)</span></p>
<p class="yiv9990787954MsoNormal"> </p>
<p class="yiv9990787954MsoNormal">We have our storage under Linux Device-Mapper Multipath control (two device paths to all storage, active/passive) and are accessible under /dev/mapper, but the NSD types are current set to ‘generic’ not ‘dmm’. This is configured in the
/var/mmfs/etc/nsddevices file:</p>
<p class="yiv9990787954MsoNormal"> </p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;">if [[ $osName = Linux ]]</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;">then</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"> : # Add function to discover disks in the Linux environment.</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"> ls -l /dev/mpath/ 2>/dev/null | awk '{print "mpath/"$9 " generic"}'</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"> ls -l /dev/mapper/ 2>/dev/null | awk '{print "mapper/"$9 "
<span style="background:yellow;">generic</span>"}'</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;"> ls -1 /dev/vd* 2>/dev/null | awk -F '/' '{print ""$3 " generic"}'</span></p>
<p class="yiv9990787954MsoNormal"><span style="font-size:10.0pt;">fi</span></p>
<p class="yiv9990787954MsoNormal"> </p>
<p class="yiv9990787954MsoNormal">Can somebody from IBM explain what the correct setting should be and what differences GPFS does with ‘generic’ vs. ‘dmm’ vs. others?</p>
<p class="yiv9990787954MsoNormal"> </p>
<p class="yiv9990787954MsoNormal">Thanks in advance!</p>
<p class="yiv9990787954MsoNormal">-Bryan</p>
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