Multipathing Configuration.

Latest response

Hi All,

I have a Dell Server where I did connect a storage back to back. And presented six 597G Luns. and configured Multipathing. Not sure if this set up right. And when I do run this command I do get this output.
fdisk -l| grep Disk\ \/dev
Disk /dev/sda: 119.5 GB, 119453777920 bytes
Disk /dev/sdb: 898.3 GB, 898319253504 bytes
Disk /dev/mapper/vg_uscsrvpdb01-lv_root: 52.1 GB, 52080672768 bytes
Disk /dev/mapper/vg_uscsrvpdb01-lv_swap: 67.1 GB, 67108864000 bytes
Disk /dev/mapper/vg_db-lv_db: 898.3 GB, 898315059200 bytes
Disk /dev/sdc: 597.0 GB, 597000454144 bytes
Disk /dev/sdd: 597.0 GB, 597000454144 bytes
Disk /dev/sde: 597.0 GB, 597000454144 bytes
Disk /dev/sdf: 597.0 GB, 597000454144 bytes
Disk /dev/sdg: 597.0 GB, 597000454144 bytes
Disk /dev/sdh: 597.0 GB, 597000454144 bytes
Disk /dev/sdi: 597.0 GB, 597000454144 bytes
Disk /dev/sdk: 597.0 GB, 597000454144 bytes
Disk /dev/sdj: 597.0 GB, 597000454144 bytes
Disk /dev/sdm: 597.0 GB, 597000454144 bytes
Disk /dev/sdl: 597.0 GB, 597000454144 bytes
Disk /dev/sdn: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathab: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathaa: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathac: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathad: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathae: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathaf: 597.0 GB, 597000454144 bytes

And when I do multipath -ll command I do see this.

multipath -ll
May 16 13:36:32 | /etc/multipath.conf line 15, invalid keyword: devnode
mpathaf (36782bcb00014e0e300003d7557356cfa) dm-8 DELL,MD32xxi
size=556G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=14 status=active
| - 14:0:0:5 sdm 8:192 active ready running-+- policy='round-robin 0' prio=9 status=enabled
- 13:0:0:5 sdn 8:208 active ready running
mpathae (36782bcb00014e0e300003d7b57356d36) dm-7 DELL,MD32xxi
size=556G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=14 status=active
|
- 14:0:0:4 sdk 8:160 active ready running
-+- policy='round-robin 0' prio=9 status=enabled- 13:0:0:4 sdl 8:176 active ready running
mpathad (36782bcb00014e0e300003d7957356d24) dm-6 DELL,MD32xxi
size=556G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=14 status=active
| - 14:0:0:3 sdi 8:128 active ready running-+- policy='round-robin 0' prio=9 status=enabled
- 13:0:0:3 sdj 8:144 active ready running
mpathac (36782bcb00014e0e300003d7757356d14) dm-5 DELL,MD32xxi
size=556G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=14 status=active
|
- 14:0:0:2 sdg 8:96 active ready running
-+- policy='round-robin 0' prio=9 status=enabled- 13:0:0:2 sdh 8:112 active ready running
mpathab (36782bcb00014e0e300003d7357356cde) dm-4 DELL,MD32xxi
size=556G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=14 status=active
| - 14:0:0:1 sde 8:64 active ready running-+- policy='round-robin 0' prio=9 status=enabled
- 13:0:0:1 sdf 8:80 active ready running
mpathaa (36782bcb00014e0e300003d7057356c76) dm-3 DELL,MD32xxi
size=556G features='3 queue_if_no_path pg_init_retries 50' hwhandler='1 rdac' wp=rw
|-+- policy='round-robin 0' prio=14 status=active
|
- 14:0:0:0 sdc 8:32 active ready running
-+- policy='round-robin 0' prio=9 status=enabled- 13:0:0:0 sdd 8:48 active ready running

My question is:
Is it ok that I'm seeing /dev/sd* disk when I'm running fdisk command or it mean that I do configure multipathing wrongly?

Disk /dev/sdd: 597.0 GB, 597000454144 bytes
Disk /dev/sdc: 597.0 GB, 597000454144 bytes
Disk /dev/sde: 597.0 GB, 597000454144 bytes
Disk /dev/sdf: 597.0 GB, 597000454144 bytes
Disk /dev/sdg: 597.0 GB, 597000454144 bytes
Disk /dev/sdh: 597.0 GB, 597000454144 bytes
Disk /dev/sdi: 597.0 GB, 597000454144 bytes
Disk /dev/sdj: 597.0 GB, 597000454144 bytes
Disk /dev/sdk: 597.0 GB, 597000454144 bytes
Disk /dev/sdm: 597.0 GB, 597000454144 bytes
Disk /dev/sdl: 597.0 GB, 597000454144 bytes
Disk /dev/sdn: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathaa: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathab: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathac: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathad: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathae: 597.0 GB, 597000454144 bytes
Disk /dev/mapper/mpathaf: 597.0 GB, 597000454144 bytes

Thanks for help.

Responses

Yes, that's the expected output. You use /dev/mapper/mpath* for disk I/O and device-mapper handles sending the I/O down the right /dev/sd* path, plus load balancing, handling failover, timing out I/O or not, etc.

Don't forget to change your LVM filter to use only the root block device(s) and /dev/mapper/mpath*. You don't want LVM to be using an individual path then have that path fail.

You can read multipath.conf.annotated in the device-mapper-multipath package and the Multipath product documentation to understand how to configure load balancing, failover times, and failover behaviour.

Jamie,

Thank you very much for your response. Much appreciated.

These mpath* are will be used by ASM. But for some reason when I see /dev/sd* on the fdisk -l command. I thought multipathing was not configured right. But since you said it's expected output it made me feel a bit better.

Thanks

We have updated mulipath configuration in redhat 7.3 as below for two servers. We want to know the it is configured correctly in each server.

We found wwid got matching with alias on each server, but dm-X (dm-number like dm-4) is different in each server. Please check this is correct.

please check the below out put on each server

[root@db1 ~]# multipath -ll | grep dm- redodg03 (3600a098038304268375d4c5635434c4c) dm-4 NETAPP ,LUN C-Mode redodg02 (3600a098038304268375d4c5635434c4b) dm-8 NETAPP ,LUN C-Mode redodg01 (3600a098038304268375d4c5635434c4a) dm-5 NETAPP ,LUN C-Mode

[root@db2 ~]# multipath -ll | grep dm- redodg03 (3600a098038304268375d4c5635434c4c) dm-8 NETAPP ,LUN C-Mode redodg02 (3600a098038304268375d4c5635434c4b) dm-6 NETAPP ,LUN C-Mode redodg01 (3600a098038304268375d4c5635434c4a) dm-7 NETAPP ,LUN C-Mode

Close

Welcome! Check out the Getting Started with Red Hat page for quick tours and guides for common tasks.