The Multi-Pathing Driver

• In a high-availability environment, administrators make sure there is more then one path to access a physical disk.
• For example, in a SAN, the host might be connected to the RAID via two separate switches.
• On the block device level, each path will look like a separate disk.
• The multi-pathing driver has the purpose of identifying that several block device actually map to the same disk, combine them to a single multipath device, and allow I/O to this device.
• When I/O gets to a multipath device, it may be sent via a single path, or using round-robin on several paths, etc.
• The multi-path driver may be controlled using the 'multipath' utility, and the /etc/multipath.conf configuration file, to support different types of multi-path devices and RAIDs.

Originally written by guy keren