HP XP P9500 Hitachi Dynamic Link Manager Software User Guide for VMWare (HIT52 - Page 34

Monitoring Intermittent Errors, Setting Up Intermittent Error Monitoring

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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 offline (Places Paths Offline) on page 6-7. A path that is recovered from an error by the automatic failback function is automatically placed in online status. When you are using intermittent error monitoring, the path in which the intermittent error occurred is not automatically placed online 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. Monitoring Intermittent Errors An intermittent error refers to an error that occurs irregularly because of something like a loose cable. In the event of an intermittent error, automatic failback will repeatedly occur causing I/O performance to drop. 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. 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. Failbacks are not performed for such paths. This status is referred to as the not subject to auto failback status. Checking Intermittent Errors You can check the paths in which intermittent errors have occurred by viewing the execution results of the HDLM command's view operation. For details on the view operation, see view (Displays Information) on page 6-22. Setting Up Intermittent Error Monitoring When you enable the intermittent error monitoring function, specify the following monitoring conditions: the error monitoring interval, and the number of times that the error needs to occur. If an error occurs on a particular path the specified number of times within the specified errormonitoring interval, then an intermittent error will occur on the path. For example, if you specify 30 for the error monitoring interval and 3 for the number of times that the error needs to occur, the path is determined to have an intermittent error if an error occurs 3 or more times in 30 minutes. 2-16 HDLM Functions Hitachi Dynamic Link Manager User Guide (for VMware(R))

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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
offline (Places Paths Offline) on page
6-
7
. A
path that is recovered from an error by the automatic failback function is
automatically placed in online status.
When you are using intermittent error monitoring, the path in which the
intermittent error occurred is not automatically placed online 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.
Monitoring Intermittent Errors
An intermittent error refers to an error that occurs irregularly because of
something like a loose cable. In the event of an intermittent error, automatic
failback will repeatedly occur causing I/O performance to drop. 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
.
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. Failbacks are not performed for such paths. This status
is referred to as the
not subject to auto failback
status.
Checking Intermittent Errors
You can check the paths in which intermittent errors have occurred by
viewing the execution results of the HDLM command's
view
operation.
For details on the
view
operation, see
view (Displays Information) on page
6-
22
.
Setting Up Intermittent Error Monitoring
When you enable the intermittent error monitoring function, specify the
following monitoring conditions: the error monitoring interval, and the
number of times that the error needs to occur. If an error occurs on a
particular path the specified number of times within the specified error-
monitoring interval, then an intermittent error will occur on the path. For
example, if you specify 30 for the error monitoring interval and 3 for the
number of times that the error needs to occur, the path is determined to
have an intermittent error if an error occurs 3 or more times in 30 minutes.
2-16
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for VMware(R))