When you create a , you specify where to create the , its capacity, its warning, and other parameters. The capacity of the flashcopy repository logical drive is created as a percentage of the and contains the data. The storage management software provides a warning message when your flashcopy repository logical drive exceeds the
threshold level.
Keep these guidelines in mind when you maintain flashcopy logical drives:
The failure policy for the flashcopy repository logical drive determines what happens when the flashcopy repository logical
drive becomes full, that is, all of its capacity has been used. You can set the failure policy to either fail the flashcopy,
which is the default setting, or fail incoming I/O to the base logical drive of the flashcopy.
Do not ignore the “threshold exceeded” notification for the flashcopy repository logical drive. This message is the last and
only warning that you will receive before the flashcopy repository logical drive becomes full. You can either increase the
capacity of the flashcopy repository logical drive or increase the threshold capacity warning level of the flashcopy repository
logical drive. If you increase the warning threshold, it reduces the time that you have to respond the next time you receive
a threshold exceeded notification.
A flashcopy logical drive or a flashcopy repository logical drive is sometimes shown as a . In this case, the has detected disk drives associated with flashcopy logical drive or flashcopy repository logical drive that are no longer
accessible. Missing logical drives are usually recoverable. For more information, refer to the Learn About Missing Logical
Drives online help topic.
When you monitor a flashcopy logical drive for performance, you do not receive a cache hit percentage, because physical cache
does not exist on the flashcopy. The physical cache exists on the base logical drive and the flashcopy repository logical
drive. If you are monitoring total I/O per , and the controller owns flashcopy logical drives, the total I/O includes reads and host writes to the flashcopy logical drive. The total I/O also includes controller read activity and controller
write activity to the associated base logical drive and flashcopy repository logical drive.
Logical drive thrashing is a condition where logical drive ownership moves from one controller to a second controller, and
back to the first controller. Logical drive thrashing occurs if a base logical drive and its associated flashcopy logical
drive are mapped to different hosts, with a different preferred path assigned on each host. This situation occurs in a NetWare
environment, an HP-UX environment, or a Linux environment when is enabled, or in a Linux server cluster environment. Logical drive thrashing can lead to degraded system performance. To
avoid logical drive thrashing, the base logical drive and the flashcopy logical drive must have the same preferred path when
mapped to one or more hosts.
Setting Options for the FlashCopy Repository Logical drive
The default capacity of a flashcopy repository logical drive is set to 20 percent of the base logical drive if enough free
capacity exists to create a flashcopy repository of this size. The default threshold level for the flashcopy repository logical
drive is set to 50 percent. If you are not sure how large to make the flashcopy repository logical drive or how high to set
the full warning for the flashcopy repository logical drive, accept the default settings. You can estimate later how quickly
the capacity of the flashcopy repository logical drive is being used. For more information, refer to the Learn About Estimating
FlashCopy Repository Logical Drive Life Expectancy online help topic.
Failure Settings for FlashCopy Logical Drives
Keep these guidelines in mind when you work with flashcopy logical drives:
If you delete a flashcopy logical drive, the associated flashcopy repository logical drive is automatically deleted.
If you delete a flashcopy repository logical drive, the associated flashcopy logical drive is automatically deleted.
If you delete a flashcopy logical drive and then create it again, you must stop the host software application. In addition,
you must unmount the base logical drive while the flashcopy logical drive is being created again.
If you re-create a flashcopy logical drive, you alleviate the need to create a flashcopy repository logical drive. This action
also alleviates the need to remap the assigned between the flashcopy logical drive and the host.
After the flashcopy logical drive is re-created, you can change parameters on the flashcopy repository logical drive through
the appropriate menu options.
To avoid another “flashcopy repository logical drive capacity full” failure, increase the capacity of the flashcopy repository
logical drive. For more information, refer to the Increasing the Capacity of a FlashCopy Repository Logical Drive online help
topic.
To view the current failure settings, perform these steps:
In the Logical pane of the Logical/Physical tab, select a flashcopy repository logical drive.
Select Logical Drive >> Properties.
To view the currently defined settings, select the Capacity tab.
If the flashcopy repository logical drive is set to fail the flashcopy logical drive when it becomes full, its data is not
recoverable. You cannot access the flashcopy. The only available option (if this situation occurs) is to either delete the
flashcopy logical drive or re-create the flashcopy logical drive to create a new point-in-time image. For more information,
refer to the Increasing the Capacity of a FlashCopy Repository Logical Drive online help topic.
If the flashcopy repository logical drive is set to fail writes to the base logical drive, the data is recoverable. However,
you must increase the capacity of the flashcopy repository logical drive before writes to the base logical drive are not rejected.