Multipath I/O
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In computer storage, multipath I/O is a fault tolerance technique whereby there is more than one physical path between the CPU in a computer system and its mass storage devices through the buses, controllers, switches, and bridge devices connecting them.
A simple example would be a SCSI disk connected to two SCSI controllers on the same computer or a disk connected to two Fibre Channel ports. Should one controller, port or switch fail, the operating system can route I/O through the remaining controller transparently to the application, with no changes visible to the applications, other than perhaps incremental latency.
Multipath software layers can leverage the redundant paths to provide performance enhancing features, such as dynamic load balancing or traffic shaping.
Multipath I/O implementations
Some operating systems support multipath I/O natively:- AIX - MPIO Driver, AIX 5L 5.2 (October 2002) and later
- Linux - multipath driver. Linux kernel 2.4.17
- Solaris Multiplexed I/O (MPxIO), Solaris 8 (February 2000) and later
- Windows MPIO Driver, Windows Server 2003 (April 2003)
- EMC Powerpath
- FalconStor IPStor DynaPath
- Fujitsu Siemens MultiPath for Linux and Windows OS
- Hitachi HiCommand Dynamic Link Manager (HDLM)
- HP Secure Path
- NCR UNIX MP-RAS EMPATH for EMC Disk Arrays
- NCR UNIX MP-RAS RDAC for Engenio Disk Arrays
- ONStor SDM multipath
- IBM TotalStorage Multipath Subsystem Device Driver (SDD), formerly Data Path Optimizer
- SUN Multipath failover driver for Windows and AIX
- SUN StorEdge Traffic Manager Software, included in Sun Java StorEdge Software suite
- Linux
- * multipath-tools, first released on September 2003
- * Fibreutils package for QLogic HBAs
- * [lpfcdriver] package for Emulex HBAs
- Veritas
- * Veritas Storage Foundation (VxSF)
- * Veritas Volume Manager (VxVM)
- Pillar Data Systems
- * Axiom Path Manager for AIX, Windows, Linux, and Solaris
External links
- [Linux Multipathing], Linux Symposium 2005 p. 147
See also
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