Multipathing

Multipathing Overview
A path is a connection between a server and the underlying storage. The path can be severed due to many reasons like faulty HBA, faulty cable etc. To avoid such single point of failures, multipathing exists. Multipathing ensures that the system uses multiple physical paths to provide redundancy and increased throughput. There are many vendor specific multipathing implementations like EMC’s powerpath and Symantecs VxDMP.
What is Device Mapper multipath
Device Mapper Multipathing (or DM-multipathing) is a Linux native multipath tool, which allows you to configure multiple I/O paths between server nodes and storage arrays into a single device. These I/O paths are physical SAN connections that can include separate cables, switches, and controllers. Multipathing aggregates the I/O paths, creating a new device that consists of the aggregated paths. Regardless of the vendor hardware in use, device mapper creates a block device under /dev/mapper/ for each LUN attached to the system.
Device Mapper components
The important components of Device Mapper multipathing are :