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Estimate Future Backup Space Requirements

CA ARCserve D2D provides you with this tool to calculate the estimated amount of available free space that you will need for backups. The calculations are based on your estimate of future data change and on the space that is occupied from previous backups.

To use this estimating tool

1. Select the backup source. This can be your entire machine or selected volumes within your machine.

   The actual size of the selected backup source is displayed in the Total Source Size field.

2. Estimate the anticipated Change Rate for future backups.

   Base this estimate upon past performance of how much your total backup size has changed for each subsequent incremental backup.

   With the Estimated Values defined, CA ARCserve D2D calculates and displays the estimated backup size required based on the configuration of the backup destination and the recovery points. The pie chart also displays the amount of used space and free space.

3. Estimate the Space Saved After Compression percentage value.

   Estimated Values

   You can use estimated values to calculate the approximate overall backup size that is based on the number of recovery points. Base this estimate upon past performance of your backups with different Compression settings applied. As you change this value, you will see the corresponding size impact for your backup sizes.

   Note: If necessary, you can perform some Full Backups, each with a different Compression setting (No Compression, Standard Compression, and Maximum Compression) to establish past performance values and help you to better calculate the percent of space saving that each setting produces for your backup.

   • Space Saved After Compression

     This value indicates how much disk space is saved after compression.

     Example: If the data size of a volume is 1000 MB and after backup the compressed data size is 800 MB, then the Space Saved After Compression is estimated to be 200 MB (20%).

   • Change Rate

     This value indicates the typical data size of an incremental backup.

     Example: If an incremental backup data size is 100 MB and the full backup data size is 1000 MB, the change rate is estimated to be 10%.

   Estimated Backup Size

   Displays the estimated values for Total Source Size, Compressed Full Backup Size, Compressed Incremental Backup Size, and Estimated Total Backup Size.

   • The Compressed Full Backup Size field displays a calculated value that is based upon:
     • Size of the backup source
     • Specified compression percentage.
   • The Compressed Incremental Backup Size field displays a calculated value that is based upon:
     • Estimated Change Rate
     • Number of recovery points to be saved
     • Specified compression percentage
   • The Estimated Total Backup Size field will display the anticipated space that you will need for future backups and is based upon:
     • Amount of space that is required for one Full Backup plus
     • Amount of space that is required for the number of Incremental Backups needed to satisfy the specified number of saved recovery points.
4. From this Estimated Total Backup Size value, you should be able to determine if your backup destination has sufficient space to fit your backup.

   If your destination does not have sufficient free space, you can consider the following corrective actions:

   • Reduce the number of saved recovery points.
   • Increase the available free space at the backup destination.
   • Change the backup destination to a larger capacity.
   • Reduce the size of the backup source (maybe eliminate unnecessary volumes from the backup).
   • Increase the Compression setting of the backup.