Estimating how large a volume needs to be

Before you create a volume, you can estimate how large it needs to be. The method you use to estimate the volume size depends on whether you need to create Snapshot copies of the volume.

Steps

1. Estimate the size of the data that will be contained in the volume as described in "Calculating the total data size".
2. Compute the estimated volume size using the appropriate procedure depending on whether you are using Snapshot copies.

   If you are using...	Use this procedure...
   Snapshot copies	Determining the volume size and fractional reserve setting when you need Snapshot copies
   No snapshot copies	Determining the volume size when you do not need Snapshot copies

• Calculating the total data size
  Determining the total data size—the sum of the sizes of all of the space-reserved LUNs or files in the volume—helps you estimate how large a volume needs to be.
• Determining the volume size and fractional reserve setting when you need Snapshot copies
  The required volume size for a volume when you need Snapshot copies depends on several factors, including how much your data changes, how long you need to keep Snapshot copies, and how much data the volume is required to hold.
• Determining the volume size when you do not need Snapshot copies
  If you are not using Snapshot copies, the size of your volume depends on the size of the LUNs and whether you are using traditional or FlexVol volumes.