Multipath I/O

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In computer storage, multipath I/O is a fault-tolerance and performance-enhancement technique that defines 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.

As an example, a SCSI hard disk drive may connect to two SCSI controllers on the same computer, or a disk may connect to two Fibre Channel ports. Should one controller, port or switch fail, the operating system can route the I/O through the remaining controller, port or switch transparently and with no changes visible to the applications, other than perhaps resulting in increased latency.

Multipath software layers can leverage the redundant paths to provide performance-enhancing features, including dynamic load balancing, traffic shaping, automatic path management, and dynamic reconfiguration.

Software implementations[edit]

  • EMC PowerPath - Multipathing support for EMC external storage including VNX family, Symmetrix family and VPLEX, on AIX, HP-UX, Linux, Solaris and Windows, plus Hyper-V and VMWare in the PowerPath/VE product.[1]
  • Symantec Veritas Dynamic Multipathing (VxDMP) - a component of Veritas Storage Foundation or of Veritas Volume Manager, also sold as a separate product since Sept, 2010. An advantage of DMP is that it is neutral to storage vendor. As of version 6.1 it was supported on AIX, Linux, OracleVM, Solaris (SPARC), VMWare and 64-bit Windows, previous versions were additionally supported on Solaris (x86) and HP-UX.[2]
  • AIX - MPIO Driver, AIX 5L 5.2 (October 2002) and later. AIX6 uses SDDPCM (Subsystem Device Driver Path Control Module), it is a modular system similar to DM-Multipath (Linux Native).
  • HP-UX 11.31 (2007) (HP Native Multipathing aka Agile I/O Mass storage) | 11.21 PV-Link (LVM native path failover)
  • Linux - Device-Mapper Multipath. Linux kernel 2.6.13 (August 2005)
  • OpenVMS V7.2 (1999) and later
  • SGI IRIX - using the LV, XLV and later XVM volume managers (1990s and onwards)
  • Solaris Multiplexed I/O (MPxIO), Solaris 8 (February 2000) and later
  • Windows Server 2008 (February 2008) and later (Although Microsoft offered a multipath IO driver since (September 2002) for Windows 2000 server and later ; but it was not integrated in OS until windows server 2008)
  • FreeBSD - GEOM_MULTIPATH and GEOM_FOX modules
  • OpenBSD - mpath(4)
  • NetBSD - using devicemapper from Linux (dm(4))
  • Mac OS X Leopard and Mac OS X Leopard Server 10.5.2
  • Novell NetWare 6.5 (July 2003)
  • VMware Native multipathing plug-in (NMP)

Multipath software products:

See also[edit]

References[edit]

External links[edit]