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 vxdmp(7)			  VxVM 3.5			    vxdmp(7)
				 1 Jun 2002



 NAME
      vxdmp - VERITAS Volume Manager multipathing disk devices

 DESCRIPTION
      Multipathed disk devices in VERITAS Volume Manager (VxVM) represent
      virtual devices with one or more physical access paths to a physical
      disk.  The Multipathing feature provides disk access reliability by
      dynamically switching to another physical path if there is a path
      failure.

      Every disk that is visible to VxVM is represented by a multipath
      device node in the /dev/vx/dmp and /dev/vx/rdmp directories for block
      type and character type interfaces.  A simple disk is represented by a
      multipath device having one physical path, whereas a disk that is part
      of a multiported disk array is represented by a multipath device with
      many device access paths depending upon the type of the disk array.

      VxVM uses standard disk device naming conventions to name multipath
      devices.	For example, if there is a disk device with two physical
      access paths such as c1t0d0 and c2t0d0, the multipathing device node
      for this particular disk is created under /dev/vx/dmp and /dev/vx/rdmp
      as c1t0d0 or c2t0d0.

      To provide multipathing, VxVM maintains an internal database of all
      the multipathed devices detected by the system and their respective
      paths.  The database is created at system boot time.  When disks are
      added or removed from the system, VxVM provides support to reconfigure
      the multipath device database to reflect new states of the hardware,
      while the system is online.

      To reconfigure the DMP database, run ioscan followed by insf, and then
      invoke vxdctl enable (see vxdctl(1M)).

      The various access paths to a multipathed device can be seen by using
      a vxdisk command (see vxdisk(1M)).  These commands open the
      multipathing configuration device /dev/vx/dmpconfig to obtain the
      required information about the various paths to a multipathed device
      and their states.

      VxVM also provides the facility to enable or disable a disk
      controller. This feature can be used to stop all I/Os through a
      particular controller to perform maintenance operations on it.  Use
      the vxdmpadm command to do this and also perform other operations on
      the multipath device database.

      VxVM can provide notification about events that occur in the DMP
      database due to a change in hardware.  See the vxnotify(1M) man page
      for more information.

      VxVM is capable of multipathing both Active/Active and Active/Passive
      disk arrays.



				    - 1 -	  Formatted:  August 2, 2006






 vxdmp(7)			  VxVM 3.5			    vxdmp(7)
				 1 Jun 2002



 FILES
      /dev/vx/dmp		    Multipathing block devices.

      /dev/vx/rdmp		    Multipathing character devices.

 SEE ALSO
      ioctl(2), vxdctl(1M), vxdisk(1M), vxdmpadm(1M), vxnotify(1M)















































				    - 2 -	  Formatted:  August 2, 2006