The following figure shows user data that is being overwritten three times (default value for number of overwrites). Volume Shredder overwrites data using the following dummy data values:

• The first overwrite is 00.
• The second overwrite is FF.
• The third overwrite is 00.

You can configure Volume Shredder to overwrite data from three to eight times, and each time the system overwrites the data you can configure the dummy data to be any hexadecimal number from 0 to FFFF.

After the system finishes overwriting data, you can view the results in the user interface or, if configured, you can open the compressed results files.

We recommend that you execute the shredding function at times of day when the host I/O load is lowest. If the number of LDEVs to be shredded is large, shredding operations might affect host I/O operations.

Use the following formula to determine the standard required time for a shredding operation.

(time required for shredding) = (time required for one dummy data write (standard required time)) x (number of times dummy 
data is written (n))