Automatic Path Switching; Automatic Failovers - Hitachi XP P9500 User Manual

• An error occurred on the path.
• A user executed the HDLM command's offline operation.
For details on the offline operation, see
page
For details on path statuses and the transitions of those statuses, see
Status Transition on page
Notes
Switching a reserved path might take several seconds. A reserved path is
switched in the following cases:
¢
¢

Automatic Path Switching

This section describes the automatic failover and automatic failback functions
that automatically switch paths.

Automatic Failovers

If you detect an error in a path being used, you can keep operating the
system by changing the path state to offline, and using other online paths.
This function is called automatic failover. Automatic failovers can be used for
the following levels of errors:
Critical
A fatal error that might stop the system.
Error
A high-risk error, which can be avoided by performing a failover or some
other countermeasure.
For details on error levels, see
When the Thunder 9500V series, or Hitachi AMS/WMS series is being used,
HDLM will select the path to be used next from among the various paths that
access the same LU, starting with owner paths, and then non-owner paths.
For example, in
controller of LU is CHA0, and access to the LU is made only via the physical
path (A). After the access path is placed offline, the first candidate for the
switching destination is the physical path (B) and the second candidate is the
physical path (C or D).
When the Lightning 9900 Series, Lightning 9900V Series, Hitachi USP,
Universal Storage Platform V/VM, Virtual Storage Platform, Hitachi AMS2000
Series, or Hitachi SMS is being used, all the paths are owner paths. This
means that all the paths that are accessing the same LU are possible
switching destinations. For example, in
2-17, the LU is accessed using only the one physical path (A). However, after
2-16
6-6.
2-19.
The reserved path is placed offline.
An owner path is placed online when a path has been reserved while
only non-owner paths are online.
Figure 2-8 Path Switching on page
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for Solaris(R))
offline (Places Paths Offline) on
Filtering of Error Information on page
Figure 2-8 Path Switching on page
Path
2-30.
2-17, the owner