What is Dynamic Multipathing (DMP)?
DMP is a method of providing two or more hardware paths to a single drive. For example, the physical hardware can have at least two paths, such as c1t1d0 and c2t1d0, directing I/O to the same drive. VxVM arbitrarily selects one of the two names and creates a single device entry, then transfers data across both paths to spread the I/O, DMP is enabled by default. Volume Manager detects multipath systems with the Universal Worldwide Device Identifiers(WWD IDs) and manages multipath targets, such as disk arrays, which define policies for using more than one path.
Benefits of DMP
The disk paths can be in a active/active (use both paths) or active/passive state (use one path).
|list controllers||vxdmpadm listctlr all|
|list enclosures||vxdmpadm listenclosure all
vxdmpadm listenclosure <enclosure>
|Display Paths||vxdmpadm getsubpaths ctlr=fscsi2
vxdmpadm getsubpaths dmpnodename=<dmp-device-name>
|Who controls the path||vxdmpadm getdmpnode nodename=c3t2d0
vxdmpadm getdmpnode enclosure=<enclosure>
|Controller (enable/disable)||vxdmpadm disable ctlr=<controller>
vxdmpadm enable ctlr=<controller>
|Statistics||vxdmpadm iostat start
vxdmpadm iostat reset
vxdmpadm iostat show all
|I/O balancing & load||
vxdmpadm getattr enclosure <enclosure> iopolicy
vxdmpadm setattr enclosure <enclosure> iopolicy=<policy>
vxdmpadm setattr path <path-name> pathtype=<path-type>
|Displays the restore/error daemon||vxdmpadm stat restored
vxdmpadm stat errord
|Starts the restore daemon||vxdmpadm start restored|
|Stops the restore daemon||vxdmpadm stop restored|