Dell PowerVault MD3820f - Manual (Page 195)

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Device Mapper Multipath For Linux
Overview
The MD Series storage arrays use a Linux operating system software framework, known as Device Mapper
(DM), to enable multipath capabilities on Linux Host Servers. The DM multipath functionality is provided
by a combination of drivers and utilities. This chapter describes how to use those utilities to complete the
process of enabling MD Series storage arrays on a Linux system.
NOTE: The required Device Mapper software components are installed on a Linux host server by
running the MD Series storage arrays resource DVD installation program on the server, and selecting
either the Full or Host install option. For detailed installation procedures, see the storage array’s
Deployment Guide at dell.com/support/manuals.
Benefits of using DM Multipath include:
• Detects path failure and re-routes I/O to other available paths
• Revalidates failed paths after path restoration
• Utilizes multiple available paths to maximize performance
• Reconfigures path usage based on path states and error conditions
• Unifies multiple device nodes into a single logical multipath device node
• Indentifies a new multipathed LU and automatically configures a new multipath node
• Provides device name persistency for DM devices under /dev/mapper/
Using DM Multipathing Devices
NOTE: Using or modifying any nodes other than the multipathing device nodes can result in array or
file system problems, including loss of communication with the array and corruption of the file
system. Avoid accessing any device other than the multipathing device.
NOTE: After creating a partition on a multipathing device, all I/O operations, including file system
creation, raw I/O and file system I/O, must be done through the partition node and not through the
multipathing device nodes.
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