Hitachi XP P9500 User Manual page 50

2. HDLM Functions
For details on error levels, see 2.11.2 Filtering of Error Information.
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
Figure 2-10: Path Switching, 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 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
Figure 2-10: Path Switching, 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).
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