Hitachi XP P9500 User Manual page 30

When the 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 Figure 2-8 Path Switching on page 2-12, the owner
controller of an LU is CHA0, and access to the LU is made via only one path
(A). After that access path (A) is placed offline, the first choice for the
switching destination is the other path connected to CHA0 (B). If an error
also occurs on that path (B), then the next possibility for a path comes from
one of the two paths (C or D) connected to CHA1.
When the 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 Figure 2-8 Path Switching on page
2-12, the LU is accessed using only the one path (A). However, after that path
is placed offline, the switching destination can come from any of the other
three paths (B, C, or D).
Figure 2-8 Path Switching
2-12
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for VMware(R))