Why use multipath

To avoid such single point of failures, multipathing exists. Multipathing ensures that the system uses multiple physical paths to provide redundancy and increased throughput. Device Mapper components The important components of Device Mapper multipathing are :. Make sure the lines in bold are commented out in order to enable device mapper. Before starting to configure the multipathing, make sure the device-mapper-multipath package is installed. If not installed, install it using yum :.

If you make any changes to this file the multipath command must be run in order to reconfigure the multipathed devices. What is Multipathing? What are Uniform and Non-uniform Exports? What are Access Groups? Where are Virtual Machine Resources Located? Are there Guidelines for Configuring Storage? Understanding Repositories What are the Repository Prerequisites?

How is a Repository Organized? How is a Repository Created? What Virtual Machine Resources are in a Repository? How are Virtual Machine Templates Managed? How are Virtual Disks Managed? Can the Repository be Backed Up? How are IP Addresses Assigned? What are Server Roles?

As an example, the server in the following diagram has two HBAs, each connected to a separate Fibre Channel switch, which in turn are connected to separate controllers on the storage array. Red Hat Enterprise Linux 7 supports multipathing using the dm-multipath subsystem. This uses the kernel device mapper system to generate virtual devices, managed by the multipathd daemon and the multipath command-line tool.

Once device-mapper-multipath is installed, configured, and started, device nodes for multipathed devices will be created under two different locations. An administrator can also set custom names for multipathed devices.

These custom names are established using the alias option in the multipaths section of the multipath configuration file. Typically only one group will be active at a time, but a group can consist of multiple paths. When a group fails, the multipath daemon will switch storage traffic to a different group. To configure multipathing, first make sure that the device-mapper-multipath package is installed. The easiest way to create this file is to use the mpathconf utility.

If that file does not exist, mpathconf will create a new configuration file from scratch. To create a default configuration, and then start and enable the multipathd daemon, use the following command:.