The Multi-Pathing Driver
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- 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.