Intermittent Error Monitoring (Functionality When Automatic Failback Is Used) - Hitachi XP P9500 User Manual

#3
When an Online or Offline(E) path exists among the paths that access the
same LU.
#4
One of the Offline(E) paths is changed to the Online(E) path.
#5
When an Offline(E) path exists among the paths that access the same LU.
The last available online path for each LU cannot be placed offline by
executing the offline operation. This ensures access to the LU. For details
on the offline operation, see
If none of the paths accessing a single LU are in the Online status, one of the
paths will be changed to the Online(E) status.
If you are using automatic failback, when the path recovers from an error,
HDLM automatically places the path online.
When you are using intermittent error monitoring, the path in which the
intermittent error occurred is not automatically placed online even when the
path recovers from the error. In such a case, place the path online manually.
Note
If there is a path failure immediately after a path is placed offline by using
the dlnkmgr command, Offline(C) might change to Offline(E). If an offline
operation was performed, wait for a fixed period of time (about 2
minute), check the path status by using the dlnkmgr command, and
make sure that the status has changed to Offline(C). If it is Offline(E),
retry the offline operation.
Intermittent Error Monitoring (Functionality When
Automatic Failback Is Used)
An intermittent error means an error that occurs irregularly because of, for
example, a loose cable connection. I/O performance might decrease while an
automatic failback is being performed to repair an intermittent error. This is
because the automatic failback operation is being performed repeatedly
(because the intermittent error keeps occurring). To prevent this from
happening, HDLM can automatically remove the path where an intermittent
error is occurring from the paths that are subject to automatic failbacks. This
process is called intermittent error monitoring.
We recommend that you use intermittent error monitoring along with the
automatic failback function.
A path in which an error occurs a specified number of times within a specified
interval is determined to have an intermittent error. The path where an
intermittent error occurs has an error status until the user chooses to place
the path back online. Automatic failbacks are not performed for such paths.
This status is referred to as the not subject to auto failback status.
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for Solaris(R))
offline (Places Paths Offline) on page 6-6.
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