HP Hitachi Dynamic Link Manager Software User Manual

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2. HDLM Functions

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 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 2-8: Path Switching, the owner 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

Figure 2-8: Path Switching, the LU is accessed using only the one physical path (A).

However, after that path is placed offline, the switching destination can come from any

of the other three physical paths (B, C, or D).
Paths are switched in units of physical paths. Therefore, if an error occurs in a path,

HDLM switches all the other paths that run through the same physical path.