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Dynamic Multi-Pathing 7.4.1 Administrator's Guide - Linux

Last Published: 2019-02-01

Product(s): InfoScale & Storage Foundation (7.4.1)

Platform: Linux

Displaying the paths to a disk

The vxdisk command is used to display the multi-pathing information for a particular metadevice. The metadevice is a device representation of a physical disk having multiple physical paths through the system's HBA controllers. In Dynamic Multi-Pathing (DMP,) all the physical disks in the system are represented as metadevices with one or more physical paths.

To display the multi-pathing information on a system

Use the vxdisk path command to display the relationships between the device paths, disk access names, disk media names, and disk groups on a system as shown here:
```
# vxdisk path
```
```
SUBPATH      DANAME     DMNAME     GROUP    STATE
sda          sda        mydg01     mydg     ENABLED
sdi          sdi        mydg01     mydg     ENABLED
sdb          sdb        mydg02     mydg     ENABLED
sdj          sdj        mydg02     mydg     ENABLED
 .
 .
 .
```
This shows that two paths exist to each of the two disks, mydg01 and mydg02, and also indicates that each disk is in the ENABLED state.

To view multi-pathing information for a particular metadevice

Use the following command:
```
# vxdisk list devicename
```
For example, to view multi-pathing information for the device sdl, use the following command:
```
# vxdisk list sdl
```
The output from the vxdisk list command displays the multi-pathing information, as shown in the following example:
```
Device:    sdl
devicetag: sdl
type:      sliced
hostid:    sys1
.
.
.
Multipathing information:
numpaths:   2
sdl   state=enabled     type=primary
sdp   state=disabled    type=secondary
```
The numpaths line shows that there are 2 paths to the device. The next two lines in the "Multipathing information" section of the output show that one path is active (state=enabled) and that the other path has failed (state=disabled).
The type field is shown for disks on Active/Passive type disk arrays such as the EMC CLARiiON, Hitachi HDS 9200 and 9500, Sun StorEdge 6xxx, and Sun StorEdge T3 array. This field indicates the primary and secondary paths to the disk.
The type field is not displayed for disks on Active/Active type disk arrays such as the EMC Symmetrix, Hitachi HDS 99xx and Sun StorEdge 99xx Series, and IBM ESS Series. Such arrays have no concept of primary and secondary paths.

Alternately, you can use the following command to view multi-pathing information:

# vxdmpadm getsubpaths dmpnodename=devicename

For example, to view multi-pathing information for emc_clariion0_431, use the following command:

# # vxdmpadm getsubpaths dmpnodename=emc_clariion0_431

Typical output from the vxdmpadm getsubpaths command is as follows:

NAME  STATE[A]   PATH-TYPE[M]         CTLR-NAME  ENCLR-TYPE    ENCLR-NAME    ATTRS PRIORITY
===========================================================================================
sdac  ENABLED    Active/Non-Optimized  c6        EMC_CLARiiON  emc_clariion0  -       -
sdam  ENABLED(A) Active/Optimized(P)   c6        EMC_CLARiiON  emc_clariion0  -       -
sdi   ENABLED    Active/Non-Optimized  c1        EMC_CLARiiON  emc_clariion0  -       -
sds   ENABLED(A) Active/Optimized(P)   c1        EMC_CLARiiON  emc_clariion0  -       -