Great! So this is just for selecting devices and according to my `mmlsnsd -X` output it's using the correct ones, so I can probably return to ignoring this parameter! -Bryan
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Eric Ross Sent: Thursday, January 18, 2018 2:01 PM To: gpfsug main discussion list <[email protected]> Subject: Re: [gpfsug-discuss] Question about NSD "Devtype" setting, nsddevices file Note: External Email ------------------------------------------------- Bryan, While waiting on the "official" word as to what each setting does differently, I remembered there was a brief explanation of the differences (at least of dmm vs generic) in the /var/mmfs/etc/nsddevices included with the GPFS-goodies toolkit (https://github.com/finley/GPFS-Goodies) I use to use when I was at IBM. //snip dmm vs. generic is used by GPFS to prioritize internal order of searching through available disks, then later GPFS discards other disk device names that it finds that match as the same NSD device by a different path. For this reason, dmm vs. generic is an important distinction if you are not explicitly producing the entire and exclusive set of disks that GPFS should use, as output from this script (nsddevices) _and_ exiting this script with a "return 0". -Brian Finley //end snip If I read that correctly, it would indicate GPFS uses those additional labels (at least dmm vs generic) as a mechanism to determine which device files to prefer when scanning a system and finding the same NSD available via different devices (i.e. /dev/mapper/foo vs /dev/sdq,/dev/sdx). By associating dmm with the dm-multipathed device, I guess it would just ignore the /dev/sd${foo} devices when it scans them. Also, the difference only seems to matter if you're not explicitly creating a list a Brian F. indicates. If you simply generate the list and exit (via return 0), GPFS wouldn't continue scanning, and then find the associated /dev/sd${foo} devices to begin with, and therefore wouldn't need a label like dmm to prioritize it over say a generic device. - Eric On Thu, Jan 18, 2018 at 10:59 AM, Bryan Banister <[email protected]> wrote: > Yes, just change the /var/mmfs/etc/nsddevices file so that it sets the > Devtype to the “correct” setting, for example: > > > > if [[ $osName = Linux ]] > > then > > : # Add function to discover disks in the Linux environment. > > ls -l /dev/mpath/ 2>/dev/null | awk '{print "mpath/"$9 " generic"}' > > ls -l /dev/mapper/ 2>/dev/null | awk '{print "mapper/"$9 " dmm"}' > > ls -1 /dev/vd* 2>/dev/null | awk -F '/' '{print ""$3 " generic"}' > > fi > > > > My question is what is the correct setting? > > > > And what does GPFS do differently with each setting? > > > > Thanks, > > -Bryan > > > > From: [email protected] > [mailto:[email protected]] On Behalf Of Jeffrey R. > Lang > Sent: Thursday, January 18, 2018 9:20 AM > To: gpfsug main discussion list <[email protected]> > Subject: Re: [gpfsug-discuss] Question about NSD "Devtype" setting, > nsddevices file > > > > Note: External Email > > ________________________________ > > So is there a way to change it if it’s set incorrectly? > > > > jeff > > > > From: [email protected] > [mailto:[email protected]] On Behalf Of Jim Doherty > Sent: Wednesday, January 17, 2018 6:28 PM > To: gpfsug main discussion list <[email protected]> > Subject: Re: [gpfsug-discuss] Question about NSD "Devtype" setting, > nsddevices file > > > > > > 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 > > > > [root@service5 ~]# mmlsnsd -X > > Disk name NSD volume ID Device Devtype Node name > Remarks > --------------------------------------------------------------------------------------------------- > volume1 0972B6CD587CD8E0 /dev/dm-0 dmm > service5.pok.stglabs.ibm.com server node > volume1 0972B6CD587CD8E0 /dev/dm-0 dmm > service6.pok.stglabs.ibm.com server node > volume2 0972B6CE587CD8E4 /dev/dm-4 dmm > service5.pok.stglabs.ibm.com server node > volume2 0972B6CE587CD8E4 /dev/dm-3 dmm > service6.pok.stglabs.ibm.com server node > volume3 0972B6CD587CD8E7 /dev/dm-1 dmm > service5.pok.stglabs.ibm.com server node > volume3 0972B6CD587CD8E7 /dev/dm-2 dmm > service6.pok.stglabs.ibm.com server node > volume4 0972B6CE587CF625 /dev/dm-3 dmm > service5.pok.stglabs.ibm.com server node > volume4 0972B6CE587CF625 /dev/dm-4 dmm > service6.pok.stglabs.ibm.com server node > > [root@service5 ~]# grep volume1 /var/mmfs/gen/mmsdrfs | grep SG_DISK > %%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::::: > [root@service5 ~]# > > > > If you run an tspreparedisk -s it will show you all of the paths. > > > > [root@service5 ~]# tspreparedisk -s | grep 0972B6CD587CD8E0 > 0972B6CD587CD8E0 /dev/sda generic > 0972B6CD587CD8E0 /dev/sdk generic > 0972B6CD587CD8E0 /dev/sdu generic > 0972B6CD587CD8E0 /dev/sdah generic > 0972B6CD587CD8E0 /dev/dm-0 dmm > [root@service5 ~]# > > > > Jim > > > > > > > > Jim > > On Wednesday, January 17, 2018, 5:12:10 PM EST, Bryan Banister > <[email protected]> wrote: > > > > > > Hi all, > > > > 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. > > > > 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: > > > > # Known disk types currently are: > > # > > # powerdisk - EMC power path disk > > # vpath - IBM virtual path disk > > # dmm - Device-Mapper Multipath (DMM) > > # dlmfdrv - Hitachi dlm > > # hdisk - AIX hard disk > > # lv - AIX logical volume. Historical usage only. > > # Not allowed as a new device to mmcrnsd. > > # gpt - GPFS partition on Windows disk > > # generic - Device having no unique failover or multipathing > > # characteristic (predominantly Linux devices). > > # dasd - DASD device (for Linux on z Systems) > > > > 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: > > > > if [[ $osName = Linux ]] > > then > > : # Add function to discover disks in the Linux environment. > > ls -l /dev/mpath/ 2>/dev/null | awk '{print "mpath/"$9 " generic"}' > > ls -l /dev/mapper/ 2>/dev/null | awk '{print "mapper/"$9 " generic"}' > > ls -1 /dev/vd* 2>/dev/null | awk -F '/' '{print ""$3 " generic"}' > > fi > > > > Can somebody from IBM explain what the correct setting should be and what > differences GPFS does with ‘generic’ vs. ‘dmm’ vs. others? > > > > Thanks in advance! > > -Bryan > > > > ________________________________ > > > Note: This email is for the confidential use of the named addressee(s) only > and may contain proprietary, confidential or privileged information. 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