veritas vxdmp.pdf

Veritas VXDMP

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 haveat least two paths, such as c1t1d0 and c2t1d0, directing I/O to the same drive. VxVM arbitrarily selects one of the twonames 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 managesmultipath targets, such as disk arrays, which define policies for using more than one path.

Benefits of DMP

High availability - DMP provides greater reliability through a path failover mechanism. In the event of a loss of oneconnection to a disk, the system continues to access the critical data over the other sound connections until the failedpath is replaced.Improved performance - DMP provides greater I/O throughput by balancing the I/O load uniformly across multipleI/O paths to the disk device.

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 enclosuresvxdmpadm listenclosure all

vxdmpadm listenclosure <enclosure>

Display Pathsvxdmpadm getsubpaths ctlr=fscsi2

vxdmpadm getsubpaths dmpnodename=<dmp-device-name>

Who controls the pathvxdmpadm 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>

adaptive

priority

balanced (default)

round-robin

minimumq

single-active

Path Type

vxdmpadm setattr path <path-name> pathtype=<path-type>

active

nomanual

nopreffered

primary

secondary

standby

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

Veritas VxDMP http://www.datadisk.co.uk/html_docs/veritas/veritas_vxdmp.htm

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