VERITAS Volume Manager 4.1 Administrator's Guide

Administering Dynamic Multipathing (DMP)

Administering DMP Using vxdmpadm

Chapter 3 147

Starting the DMP Restore Daemon

The DMP restore daemon re-examines the condition of paths at a speciﬁed interval. The type

of analysis it performs on the paths depends on the speciﬁed checking policy.

NOTE The DMP restore daemon does not change the disabled state of the path

through a controller that you have disabled using vxdmpadm disable.

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) if there are a large number of paths available. 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.