Estimating the FlashCopy Repository Logical Drive Life Expectancy

During the creation of a , you are asked to define the properties for the , including:

When you define the properties of the flashcopy repository logical drive, keep in mind what type of usage you have planned for the flashcopy logical drive. Understanding how the flashcopy logical drive will be used can help you to estimate the life expectancy of the flashcopy repository logical drive. If numerous I/O requests are written to the , the flashcopy repository logical drive, which contains the flashcopy data and data, could eventually exceed the base logical drive capacity if all the original data blocks are changed. The default setting suggests 20 percent of the base logical drive capacity, but this is a setting that can be fine-tuned after some usage data becomes available.

Estimating Life Expectancy


Note:

Use this procedure as a guide. You should re-evaluate the life expectancy of a flashcopy repository logical drive periodically.

  1. In the Logical pane, highlight the flashcopy repository logical drive by selecting Logical Drive >> Properties and clicking the Capacity tab.
  2. In the Logical pane, highlight the flashcopy repository logical drive by selecting View >> Go To >> FlashCopy Logical Drive .
  3. Record the day and time of the creation time stamp.
  4. Record the capacity used (GB) and the available capacity (GB).
  5. Determine the elapsed time (t) by subtracting the creation time from the current time, expressing the elapsed time in either minutes, hours, or days.

    You can now estimate the total time (Tr) that the repository is available for copy-on-write data based on the current usage. Multiply the elapsed time (t) by the available capacity (Ct), and divide the resulting number by the capacity used (Cu).

    Tr = (t*Ct)/Cu
    

    In the equation, Tr is the total time available, t is the elapsed time, Ct is the available capacity, and Cu is the used capacity.


    Note:

    The Total Time Available (Tr) indicates the total usage time for the flashcopy repository logical drive.

    Based on the results, you should now be able to make an informed decision on whether you should increase the capacity of the flashcopy repository logical drive. If the repository capacity will become 100 percent full during the expected lifetime of the flashcopy, you should 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.

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