GPFS is not using the underlying multipath device
You can view the underlying disk device where I/O is performed on an NSD disk by using the mmlsdisk command with the -M option.
The mmlsdisk command output might show
unexpected results for multipath I/O devices. For example if you
issue this command:
mmlsdisk dmfs2 -M
The system
displays information similar to:Disk name IO performed on node Device Availability
------------ ----------------------- ----------------- ------------
m0001 localhost /dev/sdb up
The following command is available on Linux only.
# multipath -ll
mpathae (36005076304ffc0e50000000000000001) dm-30 IBM,2107900
[size=10G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=8][active]
\_ 1:0:5:1 sdhr 134:16 [active][ready]
\_ 1:0:4:1 sdgl 132:16 [active][ready]
\_ 1:0:1:1 sdff 130:16 [active][ready]
\_ 1:0:0:1 sddz 128:16 [active][ready]
\_ 0:0:7:1 sdct 70:16 [active][ready]
\_ 0:0:6:1 sdbn 68:16 [active][ready]
\_ 0:0:5:1 sdah 66:16 [active][ready]
\_ 0:0:4:1 sdb 8:16 [active][ready]
The mmlsdisk output shows that I/O for NSD m0001 is being performed on disk /dev/sdb, but it should show that I/O is being performed on the device-mapper multipath (DMM) /dev/dm-30. Disk /dev/sdb is one of eight paths of the DMM /dev/dm-30 as shown from the multipath command.
This problem could occur for the following reasons:
- The previously installed user exit /var/mmfs/etc/nsddevices is missing. To correct this, restore user exit /var/mmfs/etc/nsddevices and restart GPFS.
- The multipath device type does not match the GPFS known device type. For a list of known device types, see /usr/lpp/mmfs/bin/mmdevdiscover. After you have determined the device type for your multipath device, use the mmchconfig command to change the NSD disk to a known device type and then restart GPFS.
The following output shows that device type dm-30 is dmm:
/usr/lpp/mmfs/bin/mmdevdiscover | grep dm-30
dm-30 dmm
To change the NSD device type to a known device type, create a
file that contains the NSD name and device type pair (one per line)
and issue this command:
mmchconfig updateNsdType=/tmp/filename
where
the contents of /tmp/filename are:m0001 dmm
The system displays information similar to:
mmchconfig: Command successfully completed
mmchconfig: Propagating the cluster configuration data to all
affected nodes. This is an asynchronous process.