HP XP7 Storage - Manual (Page 10)

Example of shredding data on flash drives
In this sample configuration, the flash drive capacity is 400 GB, the RAID configuration is 3D+1P,
and the LDEV capacity is 440 GB.
1.
Calculate the number of shredding operations.
[(400 Ч 3) Ч 2] / 440 = 5.45 = six times
Round up the value (5.45) to the nearest whole number. You need to overwrite the data six
times.
2. Define the shredding settings.
Refer to “Defining shredding conditions” (page 11) , enter the dummy data 00 in the text box
and add a row to the Data Pattern (User Setting) list (add rows for performing the shredding
operation six times).
3. Erase the volume data.
Refer to “Defining shredding conditions” (page 11) and execute the shredding operation.
4. Repeat steps 2 and 3 using the dummy data FF.
5. Repeat steps 2 and 3 using the dummy data 00.
For more information, see the Top window when selecting Logical Device section in the HP XP7
Provisioning for Open Systems User Guide.
Calculating the number of overwrite passes for FMDs
Because of the way space is allocated in FMDs, 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
FMDs, you need to calculate the number of times the system must overwrite the volume with dummy
data.
You must have the Storage Administrator (Provisioning) role to perform this task.
1.
Select an LDEV in Logical Device and write down its capacity and the amount of data in the
RAID configuration (found on the LDEVs tab).
Examples amounts of data in a RAID configuration:
n of RAID5(nxD + 1P)
n of RAID6(nxD + 2P)
2. Use the following formula to calculate the number of times to overwrite the data (N):
N = (User-capacity-for-Data x 2) / Capacity-of-target-volume
When the capacity of the FMD is 1,600 GB, 1,600GB x n
Example: The capacity of the FMD is 1,600 GB, the RAID configuration is 3D+1P, and the LDEV
capacity is 880 GB.
[(1,600 x 3) x 2] / 880 = 10.9 = 11 times
Round up the value (10.9) to the nearest whole number. You need to overwrite the data 11 times.
You can write dummy data up to eight times in one shredding operation. To write dummy data
nine or more times, perform the shredding operation for the volume as many times as required.
Example of shredding data on FMDs
This example assumes that the capacity of the FMD is 1,600 GB, the RAID configuration is 3D+1P,
and the LDEV capacity is 880 GB.
1.
Calculate the number of times to overwrite the data:
[(1,600 x 3) x 2] / 880 = 10.9 = 11 times
Round up the value (10.9) to the nearest whole number. You need to overwrite the data 11
times.
10 Volume Shredder operations