Regardless of the vendor hardware in use, device mapper creates a block device under /dev/mapper/ for each LUN attached to the system. Multipathing aggregates the I/O paths, creating a new device that consists of the aggregated paths. These I/O paths are physical SAN connections that can include separate cables, switches, and controllers. The first and most important reason (the most common) is the lack of a suitable software that supports DM among those that are installed on your device. What is Device Mapper multipathĭevice 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. If you cannot open the DM file on your computer - there may be several reasons. There are many vendor specific multipathing implementations like EMC’s powerpath and Symantecs VxDMP. Multipathing ensures that the system uses multiple physical paths to provide redundancy and increased throughput. To avoid such single point of failures, multipathing exists. The path can be severed due to many reasons like faulty HBA, faulty cable etc. A path is a connection between a server and the underlying storage.
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