Multipath software provides a redundant path
to the storage array in case one of the physical paths is disrupted.
The multipath software presents the operating system with a single
virtual device that represents the active physical paths to the storage.
The multipath software also manages the failover process that updates
the virtual device. You use the device mapper multipath (DM-MP) tool
for Linux installations.
Before
you begin
You have installed the required packages on your
system.
- For Red Hat (RHEL) hosts,
verify the packages are installed by running rpm -q device-mapper-multipath.
- For SLES hosts, verify
the packages are installed by running rpm -q multipath-tools.
By default, DM-MP is disabled
in RHEL and SLES. Complete the following steps to enable DM-MP components
on the host.
If you have not already installed the operating
system, use the media supplied by your operating system vendor.
- If a multipath.conf file is not already created, run the # touch
/etc/multipath.conf command.
- Use the default multipath settings
by leaving the multipath.conf file blank.
- Start the multipath service.
# systemctl start multipathd
- Configure multipath for startup
persistence.
# chkconfig multipathd on
- Save your kernel
version by running the uname -r command.
# uname -r
3.10.0-327.el7.x86_64
You will use this information when you assign volumes to
the host.
- Do one of the
following to enable the multipathd daemon on boot.
| If you are using.... |
Do this... |
|---|
| RHEL 6.x systems: |
chkconfig multipathd on |
| RHEL 7.x systems: |
systemctl enable mulipathd |
| SLES 12.x and 15.x systems: |
systemctl enable mulipathd |
- Rebuild the initramfs image or the initrd image
under /boot directory:
| If you are using.... |
Do this... |
|---|
| RHEL 6.x and 7.x systems: |
dracut --force --add multipath |
| SLES 12.x and 15.x systems: |
dracut --force --add multipath |
- Make sure that
the newly created /boot/initrams-* image or /boot/initrd-* image is selected in the boot configuration
file.
For example, for grub it is /boot/grub/menu.lst and for grub2 it is /boot/grub2/menu.cfg.
- Use the "Create
host manually" procedure in the online help to check whether the
hosts are defined. Verify that each host type is either Linux DM-MP (Kernel 3.10 or later) if you enable the
Automatic Load Balancing feature, or Linux DM-MP (Kernel
3.9 or earlier) if you disable the Automatic Load Balancing
feature. If necessary, change the selected host type to the appropriate
setting.
- Reboot the host.