vxdmp(7) VxVM 3.5 vxdmp(7)
1 Jun 2002
NAME [Toc] [Back]
vxdmp - VERITAS Volume Manager multipathing disk devices
DESCRIPTION [Toc] [Back]
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: January 24, 2005
vxdmp(7) VxVM 3.5 vxdmp(7)
1 Jun 2002
FILES [Toc] [Back]
/dev/vx/dmp Multipathing block devices.
/dev/vx/rdmp Multipathing character devices.
SEE ALSO [Toc] [Back]
ioctl(2), vxdctl(1M), vxdisk(1M), vxdmpadm(1M), vxnotify(1M)
- 2 - Formatted: January 24, 2005 [ Back ] |
