HP Hitachi Dynamic Link Manager Software User Manual

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2. HDLM Functions

For details on error levels, see 2.10.2 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 2-8: 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 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 all the paths accessing the same LU can be

possible switching destinations. For example, in Figure 2-8: Path switching, the LU

is accessed using only the path (A). After the access path is placed offline, the

switching destination is one of the paths (B), (C), and (D).
For details on the priority for determining which of the paths to the same LU is used

as the switching destination, see (2) Priority of Switching Destination Paths.