ONTAP 9.14

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Calculate rate of data growth for LUNs

You need to know the rate at which your LUN data is growing over time to determine whether you should use space-reserved LUNs or non-space-reserved LUNs.

About this task

If you have a consistently high rate of data growth, then space-reserved LUNs might be a better option for you. If you have a low rate of data growth, then you should consider non-space-reserved LUNs.

You can use tools such as OnCommand Insight to calculate your rate of data growth or you can calculate it manually. The following steps are for manual calculation.

  1. Set up a space-reserved LUN.

  2. Monitor the data on the LUN for a set period of time, such as one week.

    Make sure that your monitoring period is long enough to form a representative sample of regularly occurring increases in data growth. For instance, you might consistently have a large amount of data growth at the end of each month.

  3. Each day, record in GB how much your data grows.

  4. At the end of your monitoring period, add the totals for each day together, and then divide by the number of days in your monitoring period.

    This calculation yields your average rate of growth.


In this example, you need a 200 GB LUN. You decide to monitor the LUN for a week and record the following daily data changes:

  • Sunday: 20 GB

  • Monday: 18 GB

  • Tuesday: 17 GB

  • Wednesday: 20 GB

  • Thursday: 20 GB

  • Friday: 23 GB

  • Saturday: 22 GB

In this example, your rate of growth is (20+18+17+20+20+23+22) / 7 = 20 GB per day.

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