VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Chapter 3, Administering Dynamic Multipathing (DMP)

Administering DMP Using vxdmpadm

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Use the start restore command to start the restore daemon and specify one of the

following policies:

◆ check_all

The restore daemon analyzes all paths in the system and revives the paths that are

back online, as well as disabling the paths that are inaccessible. The command to start

the restore daemon with this policy is:

# vxdmpadm start restore policy=check_all [interval=seconds]

◆ check_alternate

The restore daemon checks that at least one alternate path is healthy. It generates a

notiﬁcation if this condition is not met. This policy avoids inquiry commands on all

healthy paths, and is less costly than check_all in cases where a large number of

paths are available. This policy is the same as check_all if there are only two paths

per DMP node. The command to start the restore daemon with this policy is:

# vxdmpadm start restore policy=check_alternate [interval=seconds]

◆ check_disabled

This is the default policy. The restore daemon checks the condition of paths that were

previously disabled due to hardware failures, and revives them if they are back

online. The command to start the restore daemon with this policy is:

# vxdmpadm start restore policy=check_disabled [interval=seconds]

◆ check_periodic

The restore daemon performs check_all once in a given number of cycles, and

check_disabled in the remainder of the cycles. This policy may lead to periodic

slowing down(due to check_all) ifthere are a large number of pathsavailable. The

command to start the restore daemon with this policy is:

# vxdmpadm start restore policy=check_periodic interval=seconds \

[period=number]

The interval attribute must be speciﬁed for this policy. The default number of

cycles between running the check_all policy is 10.

The interval attribute speciﬁes how often the restore daemon examines the paths. For

example, after stopping the restore daemon, the polling interval can be set to 400 seconds

using the following command:

# vxdmpadm start restore interval=400

The default interval is 300 seconds. Decreasing this interval can adversely affect system

performance.