Details on Configuring the /etc/multipath.conf for our Nexsan Setup

The multipath -v2 -d with our configuration gives:

[root@umfs03 ~]# multipath -v2 -d
create: mpatha (36000402002fc871c675a04d200000000) undef NEXSAN,SATABeast2
size=22T features='0' hwhandler='0' wp=undef
|-+- policy='round-robin 0' prio=1 status=undef
| `- 6:0:0:1 sdb 8:16   undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 2:0:0:1 sdi 8:128  undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 5:0:0:1 sdq 65:0   undef ready  running
`-+- policy='round-robin 0' prio=1 status=undef
  `- 7:0:0:1 sdx 65:112 undef ready  running
create: mpathb (36000402002fc871c675a04d300000000) undef NEXSAN,SATABeast2
size=22T features='0' hwhandler='0' wp=undef
|-+- policy='round-robin 0' prio=1 status=undef
| `- 6:0:0:2 sdc 8:32   undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 2:0:0:2 sdj 8:144  undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 5:0:0:2 sdr 65:16  undef ready  running
`-+- policy='round-robin 0' prio=1 status=undef
  `- 7:0:0:2 sdy 65:128 undef ready  running
create: mpathc (36000402002fc871c675a04a000000000) undef NEXSAN,SATABeast2
size=18T features='0' hwhandler='0' wp=undef
|-+- policy='round-robin 0' prio=1 status=undef
| `- 6:0:0:3 sdd 8:48   undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 2:0:0:3 sdk 8:160  undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 5:0:0:3 sds 65:32  undef ready  running
`-+- policy='round-robin 0' prio=1 status=undef
  `- 7:0:0:3 sdz 65:144 undef ready  running
create: mpathd (36000402002fc871c675a04a100000000) undef NEXSAN,SATABeast2
size=18T features='0' hwhandler='0' wp=undef
|-+- policy='round-robin 0' prio=1 status=undef
| `- 6:0:0:4 sde 8:64   undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 2:0:0:4 sdm 8:192  undef ready  running
`-+- policy='round-robin 0' prio=1 status=undef
  `- 5:0:0:4 sdt 65:48  undef ready  running
create: mpathe (36000402002fc871c675a04a200000000) undef NEXSAN,SATABeast2
size=18T features='0' hwhandler='0' wp=undef
|-+- policy='round-robin 0' prio=1 status=undef
| `- 6:0:0:5 sdf 8:80   undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 2:0:0:5 sdn 8:208  undef ready  running
`-+- policy='round-robin 0' prio=1 status=undef
  `- 5:0:0:5 sdu 65:64  undef ready  running
create: mpathf (36000402002fc871c675a04a300000000) undef NEXSAN,SATABeast2
size=18T features='0' hwhandler='0' wp=undef
|-+- policy='round-robin 0' prio=1 status=undef
| `- 6:0:0:6 sdg 8:96   undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 2:0:0:6 sdo 8:224  undef ready  running
`-+- policy='round-robin 0' prio=1 status=undef
  `- 5:0:0:6 sdv 65:80  undef ready  running
create: mpathg (36000402002fc871c675a04a400000000) undef NEXSAN,SATABeast2
size=18T features='0' hwhandler='0' wp=undef
|-+- policy='round-robin 0' prio=1 status=undef
| `- 6:0:0:7 sdh 8:112  undef ready  running
|-+- policy='round-robin 0' prio=1 status=undef
| `- 2:0:0:7 sdp 8:240  undef ready  running
`-+- policy='round-robin 0' prio=1 status=undef
  `- 5:0:0:7 sdw 65:96  undef ready  running

We need to setup appropriate aliases in /etc/multipath.conf as well as some tuning. Since we are using a 2.6.38 kernel this info from RHEL6 is relevant: http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/DM_Multipath/MPIO_Overview.html

I tried to setup the /etc/multipath.conf to use the new path_selectors: queue-lenth or service-time but our UL kernel 2.6.38-UL1 didn't have them. I re-ran the kernel build after setting the options to build these MD modules and installed them. I also used the mpathconf to setup the configuration:

[root@umfs03 linux-2.6.38.x86_64]# mpathconf 
multipath is enabled
find_multipaths is enabled
user_friendly_names is enabled
dm_multipath module is loaded
multipathd is chkconfiged on

The final /etc/multipath.conf file is available here for download if you want it.

Once we change the multipath.conf we need to restart the service: service restart multipathd. Now a bunch of news devices show up (NOTE I needed to reboot UMFS03 to get ALL the partitions to show up...one of the ones on the SATABeast2 was missing prior to reboot):

[root@umfs03 ~]# fdisk -l | grep /dev/dm
Disk /dev/dm-0: 24004.0 GB, 24003980820480 bytes
Disk /dev/dm-1: 24004.0 GB, 24003980820480 bytes
Disk /dev/dm-2: 24004.0 GB, 24003980820480 bytes
Disk /dev/dm-3: 20003.3 GB, 20003317350400 bytes
Disk /dev/dm-4: 20003.3 GB, 20003317350400 bytes
Disk /dev/dm-5: 20003.3 GB, 20003317350400 bytes
Disk /dev/dm-6: 20003.3 GB, 20003317350400 bytes
Disk /dev/dm-7: 20003.3 GB, 20003317350400 bytes

The first 3 are the RAID-6 partitions on the SATABeast2 unit, while the next 5 are the RAID-6 partitions on the B60X expansion shelf. The dmsetup command may also be helpful.

-- ShawnMcKee - 30 Apr 2011

• multipath.conf: multipath.conf from UMFS03 for Nexan SATABeast2 configuration