Hitachi Dynamic Link Manager, User Manual

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2. HDLM Functions
34
(2) When an Intermittent Error Does Not Occur
If an error does not occur on a path a specified number of times within a specified
interval, an intermittent error will not occur. In such a case, the error monitoring will
finish when the specified error-monitoring interval finishes, upon which the number of
errors is reset to 0. If an error occurs on the path again at a later time, error monitoring
will resume when the path is recovered from the error via an automatic failback.
If it takes a long time for an error to occur, an intermittent error can be more easily
detected by increasing the error-monitoring interval or by decreasing the number of
times that the error needs to occur.
Figure 2-13: What Will Happen When an Intermittent Error Does Not Occur on a
Path shows what will happen when an intermittent error does not occur. For this
example, the path is determined to have an intermittent error if the error occurs three
or more times in 30 minutes. The events that occur are described by using the time
arrows.
Figure 2-13: What Will Happen When an Intermittent Error Does Not Occur on
a Path
As shown in Figure 2-13: What Will Happen When an Intermittent Error Does Not
Occur on a Path , normally, the count for the number of times that an error occurs is
started after the path is first recovered from an error by using the automatic failback
function. However, if all the paths connected to the LU are in the
Offline(E)
,
Online(E)
, or
Offline(C)
status (which is due to the disconnection of the paths or
some other reason), the paths will not be recovered and put back online by using the
automatic failback function. If I/O operations are continuously being issued to such an
LU, the count for the number of times that the error occurs might be started even
though the path will not be placed online. If the number of times that the error occurs
reaches the specified value, the path is determined to have an intermittent error. In such
a case, remove the cause of the error, and then manually place the path online.