topic Re: How to configure redhat multipath in Operating System - Linux

How to configure redhat multipath

sen_ux — Fri, 29 Apr 2011 08:22:17 GMT

Hi All,

Please tell me the step-by-step procedure to configure redhat-multipath.. Below are the details..

Server : IBM Blade
Storage : HP EVA
OS : RedHat Enterprise Linux 5.1
Multipath rpm : device-mapper-multipath-0.4.7-12.el5
/etc/multipath.conf is attached..
Currently I have 4 paths for each LUN.
Please let me know what are the chjanges to be made to the conf file..

Let me know if you need more info...

Thanks.

Re: How to configure redhat multipath

sen_ux — Fri, 29 Apr 2011 08:25:28 GMT

I have filesystems created using sigle paths and running Oracle DB.. Can I mount the filesystems using the multipath device, after configuring ? Does this activity impact the Data ?

Thanks

Re: How to configure redhat multipath

Matti_Kurkela — Fri, 29 Apr 2011 21:51:25 GMT

> Can I mount the filesystems using the multipath device, after configuring ?

Yes you can.

> Does this activity impact the Data ?

No, not at all. After all, you're accessing the exact same LUNs: the multipath layer just chooses the path(s) used, and can retry any I/O operation using other path(s) if the original path seems to have failed.

For the configuration steps, see RedHat's DM-Multipath guide for RHEL 5:

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/index.html

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/DM_Multipath/index.html

By the way, you really should update to at least RHEL 5.3 (the current RHEL 5.x version is 5.6). The dm-multipath subsystem received some improvements in 5.2 and 5.3.

HP has also provided a "dm-multipath enablement kit" for HP EVA storage. This is important if you plan to use RHEL 5.1 or other early 5.x releases.

In RHEL 5.6 release, the configuration settings and other important parts of the enablement kit were included in the main dm-multipath package by RedHat, so the kit will eventually become unnecessary if you update your system.

http://h20000.www2.hp.com/bizsupport/TechSupport/DriverDownload.jsp?prodNameId=3559652〈=en&cc=us&taskId=135&prodTypeId=18964&prodSeriesId=3559651

MK

Re: How to configure redhat multipath

sen_ux — Sat, 30 Apr 2011 07:32:58 GMT

Hi MK,

Thank you.
Can you please confirm if I can follow below steps..

1. Edit /etc/multipath.conf
2. Save the file and exit editor.
3. Run modprobe dm-multipath
4. Run service multipathd start
5. Run multipath â v2
6. Run chkconfig multipathd on
7. Check if multipath devices are created. Use ls â l /dev/mpath* ( It should list devices )
8. Run multipath â ll to see the mappings.. ..
9. Edit /etc/fstab and comment all the filesystems using SAN.
10. Reboot the server.
11. Confirm if the service is running, service multipathd status
12. Check the device files.. ls â l /dev/mpath
13. Use multipath â ll and the old df â h output to map the corresponding multipath device file for each filesystem..

Re: How to configure redhat multipath

Matti_Kurkela — Mon, 02 May 2011 07:21:57 GMT

Your steps look OK to me.

NOTE: if your /var is a separate filesystem, you should do this procedure before rebooting with dm-multipath enabled:

mkdir /etc/multipath
mv /var/lib/multipath/bindings /etc/multipath/bindings
ln -s /etc/multipath/bindings /var/lib/multipath/

Relevant links to RedHat Knowledge Base (RHN access required):
https://access.redhat.com/kb/docs/DOC-5544
https://access.redhat.com/kb/docs/DOC-17650

MK