Using multipath for disk created on SAN

codenjanod · 07-27-2010, 10:23 AM

Hi all,

Any help would be appreciated.
I need to set up 1 disk, the disk is presented to the server on both fibre paths from the SAN.

This is the current setup seen:
fdisk -l

Code:

Disk /dev/sda: 107.3 GB, 107374510080 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sda doesn't contain a valid partition table

Disk /dev/sdb: 107.3 GB, 107374510080 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdb doesn't contain a valid partition table

Nothing is displayed in /dev
ll /dev/mapper

Code:

crw------- 1 root root 10, 63 Jan 13 04:32 control

This is running on:

Quote:

Linux server01 2.6.18-164.el5PAE #1 SMP Thu Sep 3 02:28:20 EDT 2009 i686 athlon i386 GNU/Linux

I need to set up this disk to be seen as one.

How to go about it?

Thanks.

MensaWater · 07-27-2010, 12:57 PM

Haven't used it myself as we use EMC PowerPath for multiple paths here.

However, on checking I see there is a man page for multipath itself so typing "man multipath" should give you some information.

Essentially from what I saw at an Oracle link that talked about both Multipath and PowerPath it seems the general concept is the same. You have two paths to a device and you setup a 3rd device that knows about the other 2 paths. (e.g. /dev/multipatha). (The man page mentioned above should show how to do that.) You can then partition that device and fdisk -l should show it and the two underlying devices with the same partitioning. In your mounts or applications you would want to be sure to refer to the multipath device and NOT the underlying devices so as to be sure things still work if one of your fibre paths go out.