Volume Shredder shreds an LDEV (basic volume) or Dynamic Provisioning volume by overwriting the volume three times with dummy data. This is referred to as an overwrite pass.
Because of the way space is allocated in flash drives, the dummy data that is used to overwrite the volume must exceed the capacity of the target volume. Therefore, before you shred a volume on flash drives, you need to calculate the number of times the system must overwrite the volume with dummy data, or how many overwrite passes to execute.
Use the following workflow to shred volumes:
- Calculate the number of overwrite passes required to shred the volume.
Using the drive capacity (GB) of the volume, the volume capacity (GB), and the number of drives in the parity group, calculate the number of overwrite passes required for the selected volume:
n = [(drive-capacity × number-of-drives-in-parity-group × number-of-data-drives-in-parity-group) / (number-of-data-drives-in-parity-group + number-of-parity-drives-in-parity-group) × 2] / LDEV-capacity
Example: The capacity of the flash drive is 400 GB, the RAID configuration is 6D+2P, and the volume capacity is 440 GB.
[((400 x 9 x 6) / (6+2)) x 2] / 440 = 12.27 = 13 times
Round up the value (12.27) to the nearest whole number. You need to overwrite the volume 13 times.
- Calculate the number of times the command must be executed to complete the required number of overwrite passes.
Each execution overwrites the data three times, so divide the number of overwrite passes by 3 to calculate the number of necessary command executions.
number-of-command-execution = n / 3
Round up the value to the nearest whole number. This is the number of times you should execute the shred command.
- Confirm the volume status (must be Normal).
- Block the volume to be shredded.
- Shred the volume.Note: You can stop shredding before its completion. If you stop shredding before it completes, the status of the volume remains as blocked.
When shredding is complete, the status of the volume is automatically changes to normal.
- Verify that the shred operation completed (volume status = Normal).