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Volume shredding

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Workflow for shredding

Use the following workflow to shred volumes using Volume Shredder:

  1. Verify that the current shredding status for the volume is Normal. See Viewing shredding status with the Logical Devices window.
  2. Block the volume. See Blocking a volume.
  3. Calculate the number of overwrite passes. See Calculating the number of overwrite passes for flash drives or SCMs or Calculating the number of overwrite passes for FMDs.
  4. Define the shredding conditions. See Defining shredding conditions.
  5. Shred volumes. See Shredding a volume or Shredding volumes in parity groups.

    If you need to stop a shredding operation, see Stopping a shredding operation from HDvM - SN Tasks window.

  6. Check the shredding results in the results file. See Viewing shredding results in the compressed files.
Parent Topic

Blocking a volume

Before you begin

  • You must have the Storage Administrator (Provisioning) role to perform this task.

  • Review information related to the following in the Provisioning Guide for your storage system:

    • Blocking LDEVs
    • Selecting logical devices
    • Selecting internal or external parity groups

Procedure

  1. Perform one of the following, depending on the location of the volume:

    • To display the LDEVs tab, in the Storage Systems tree, select Parity Groups, Internal, or External, and then select the parity group that contains the volume you want to block.
    • To display the LDEVs tab, in the Storage Systems tree, select Logical Devices.
    • To display the Virtual Volumes tab, in the Storage Systems tree, select Pools, and then select the pool that contains the virtual volume you want to block.

  2. Confirm the current status of the volume you want to block by viewing the Status column of the table.

    • If the volume is already blocked, Blocked appears in the status column.
    • If the volume is not blocked, a status other than Blocked appears in the status column.

  3. Select the volume you want to block, click More Actions, and then select Block LDEVs. The Block LDEVs window opens.

  4. Note the settings in the Block LDEVs window, enter a unique task name or accept the default name, and then click Apply.

    If Go to tasks window for status is selected, the Tasks window will open.
Parent Topic

Blocking volumes in a parity group

Before you begin

  • You must have the Storage Administrator (Provisioning) role to perform this task.

  • Review information related to the following in the Provisioning Guide for your storage system:

    • Blocking LDEVs
    • Selecting logical devices
    • Selecting internal or external parity groups

Procedure

  1. Display the Parity Groups tab by choosing one of the following steps, depending on the location of the parity group:

    • In the Storage Systems tree, select Parity Groups.
    • In the Storage Systems tree, select Parity Groups, and then select Internal or External.

  2. Confirm the current status of the volumes you want to block by viewing the LDEV Status column of the table.

    • If the volume is already blocked, Blocked appears in the status column.
    • If the volume is not blocked, a status other than Blocked appears in the status column.

  3. Select the parity group you want to block, click More Actions, and then select Block LDEVs. The Block LDEVs window opens.

  4. Note the settings in the Block LDEVs window, enter a unique task name or accept the default name, and then click Apply.

    If Go to tasks window for status is selected, the Tasks window will open.
Parent Topic

Calculating the number of overwrite passes for flash drives or SCMs

Because of the way space is allocated in flash drives or SCMs, 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 or SCMs, you need to calculate the number of times the system must overwrite the volume with dummy data.

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. Select an LDEV on the LDEVs tab in the Logical Devices window, and write down its capacity and the number of data drives in its parity group (for example, 3 drives for RAID5-3D+1P, 6 drives for RAID6-6D+2P).

  2. Use the following formula to calculate the number of times to overwrite the selected LDEV:

    n = [(drive-capacity × number-of-data-drives-in-parity-group) × 2] / LDEV-capacity

    Example: The capacity of the flash drive or SCM is 400 GB, the RAID configuration is 3D+1P, and the LDEV capacity is 440 GB.

    [(400 x 3) x 2 ] / 440 = 5.45 = six times

    Round up the value (5.45) to the nearest whole number. You need to overwrite the LDEV six times.

Parent Topic
Child Topics

Example of shredding data on flash drives or SCMs
In this sample configuration, the capacity of the flash drive or SCM is 400 GB, the RAID configuration is 3D+1P, and the LDEV capacity is 440 GB.

Procedure

  1. Calculate the number of shredding operations.

    [(400 × 3) × 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, 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 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.

Parent Topic

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.

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. Select an LDEV on the LDEVs tab in the Logical Devices window, and write down its capacity and the number of data drives in its parity group (for example, 3 drives for RAID5-3D+1P, 6 drives for RAID6-6D+2P).

  2. Use the following formula to calculate the number of times to overwrite the selected LDEV:

    n = [(drive-capacity × number-of-data-drives-in-parity-group) × 2] / LDEV-capacity

    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 LDEV 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.

Parent Topic
Child Topics

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.

Procedure

  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.

  2. Define the shredding settings.

    Refer to Defining shredding conditions, select the Data Pattern (User Setting) list and Random Data, then click Add eight times.

  3. Erase the volume data.

    Refer to Defining shredding conditions for procedures on erasing the volume data.

  4. Repeat steps 2 and 3, three more times, clicking Add three times.

Parent Topic

Defining shredding conditions

Configure data overwrite patterns and the number of overwrite passes in the Shredding Data Pattern window. By default the number of overwrite passes is three; but you can change this number from three to up to eight times. The system keeps user-specified settings while the Shred LDEVs window is open.

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. In the Storage Systems tree, select Logical Devices to display the LDEVs tab.

  2. Select a blocked volume, click More Actions, and then select Shred LDEVs to open the Shred LDEVs window.

  3. Click Edit Data Pattern. The Edit Shredding Data Pattern window opens.

  4. To use the default pattern, click Default Pattern (00-FF-00).

    To specify custom settings, click Data Pattern (User Setting) and specify the data pattern as follows:
    CautionFor FMDs, make sure you select Random Data as the specified Data Pattern.

    1. To add a random data pass, select Random Data, and click Add. A random data pass is added in the Data Pattern (User Setting) table.

    2. To define a data pattern, click Define Data, enter the number that you want to use as dummy data in the text box, and click Add. You can enter a hexadecimal number of up to four digits (0 to FFFF). The data pattern is added in the Data Pattern (User Setting) table.

      CautionYou should enter three or more numbers to use as dummy data. If you overwrite data with less than three numbers, some or all data might be recoverable.

    3. If you make a mistake, click Clear and re-enter the desired numbers.

  5. When the data pattern is correct (default or user-defined), click OK to save your settings and close the Edit Shredding Data Pattern window.

  6. Click Cancel to close the Shred LDEVs window.

Parent Topic

Shredding a volume

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. Choose one of the following steps, depending on the location of the volume:

    • To display the LDEVs tab, in the Storage Systems tree, select Logical Devices, or select Parity Groups, Internal, or External and then select the parity group that contains the volume you want to shred.

    • To display the Virtual Volumes tab, in the Storage Systems tree, select Pools, and then select the pool that contains the virtual volume you want to shred.

  2. Select the volume you want to shred and confirm the current status of the volume by viewing the Status column of the table.

    • If the volume is already blocked, Blocked appears in the status column.

    • If the volume is not blocked, a status other than Blocked appears in the status column. In this case, you need to block the volume before you can shred it. See Blocking a volume.

  3. Click More Actions Shred LDEVs.

  4. To save the shredding results to a file, click Set Data Output (you can output the shredding results of up to three volumes). If you don’t want to save the results to a file, click Cancel Data Output.

  5. Click Finish.

  6. Verify the settings in the Shred LDEVs window.

    When the settings are correct, enter a unique task name or accept the default name, and click Apply. If Go to tasks window for status is selected, the Tasks window will open.

  7. Check the operation results.

    After the shredding operation is completed, the volume status automatically changes from Blocked to Normal.
Parent Topic

Shredding volumes in parity groups

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. Display the Parity Groups tab by choosing one of the following steps, depending on the location of the parity group:

    • In the Storage Systems tree, select Parity Groups.
    • In the Storage Systems tree, select Parity Groups, and then select Internal or External.

  2. Select the parity group you want to shred and confirm the current status by viewing the Status column of the table.

    • If the parity group is already blocked, Blocked appears in the status column.

    • If the parity group is not blocked, a status other than Blocked appears in the status column. In this case, you need to block the parity group before you can shred it. See Blocking volumes in a parity group.

  3. Click More Actions Shred LDEVs.

  4. To save the shredding results to a file, click Set Data Output (you can output the shredding results of up to three volumes). If you don’t want to save the results to a file, click Cancel Data Output.

  5. Click Finish.

  6. Verify the settings in the Shred LDEVs window.

    When the settings are correct, enter a unique task name or accept the default name, and click Apply. If Go to tasks window for status is selected, the Tasks window will open.

  7. Check the operation results.

    After the shredding operation is completed, the volume status automatically changes from Blocked to Normal.
Parent Topic

Viewing shredding status with the Logical Devices window

You can verify the progress of shredding operations using either the Logical Devices window or the Tasks window.

Procedure

  1. In the Storage Systems tree, click Logical Devices.

  2. Verify the shredding progress in the Logical Devices window. When the volume shredding is in progress, the Status column displays Shredding.

    For details about the Logical Devices window, see the Provisioning Guide for your storage system.

Parent Topic

Viewing results
Parent Topic
Child Topics

Viewing shredding results with the Tasks window

Use the Tasks window to verify the results of the shredding operation.

NoteIf there is at least one volume specified to save the shredding results to a file, you can check the operation results in the shredding result file. For details, see Viewing shredding results in the compressed files.

Procedure

  1. In the Storage Systems tree, select Tasks.

  2. Click the task name of the desired task in the Task Name column.

  3. In the Task Properties window, view the Result column in the Shredding Data Pattern table.

    Check the contents to verify whether all the overwriting operations have been completed normally. If an overwriting pass is not completed normally, it means the shredding was not successful. If shredding fails, try shredding the volume again. If shredding fails again, contact customer support to resolve the error. If the storage system experiences a power outage during the shredding process, one of the following error messages will appear:

    • Shredding operation canceled
    • Shredding operation failed

  4. Click Close to close the Task Properties window.

    The following table lists and describes the Volume Shredder status messages that are displayed in the shredding results.

    Status Description
    -- The shredding operation was not performed.
    Shredding operation Normal. The shredding operation was successful.
    Writing. The shredding operation is in progress.
    Shredding operation not executed. The shredding operation did not occur as specified.
    Shredding operation canceled. The shredding operation was canceled, or power to the system was interrupted.
    Shredding operation Failed. The shredding operation was not successful, or power to the system was interrupted.
    Shredding data transfer error. The system could not write the shredding results to a file.
    Shredding data verify error. An error was detected in the file containing the shredding results.
    No-data assigned. When you shred an unused Dynamic Provisioning virtual volume, no dummy data is written to the volume. In this case the status of the shredding operation in the shredding results file is No-data assigned.
Parent Topic

Viewing shredding results in the compressed files

If there is at least one volume specified to save the shredding results to a file, you can save the shredding results as a compressed file on the computer. The following procedure shows how to view the shredding results in the file.

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. Display the Device Manager - Storage Navigator main window.

  2. On the menu bar, select Reports Shredding Report, and then click either Download Latest Report to download the latest result file or Download Other Reports to download the past ten times result files.

    When the preparation for download is complete, a message appears.

  3. Click OK.

  4. Specify the folder in which to download the file.

  5. Click Save.

    Compressed files are downloaded.

  6. Decompress the file. The binary file showing the results of shredding, the text file showing the contents of shredding operation, and its result are output.

  7. Check the shredding results in the decompressed files. For details, see Understanding shredding results in compressed files.

Parent Topic

Understanding shredding results in compressed files

When you open the compressed file, you see binary and text files that contain shredding results.

  • The name of the binary file indicates LDKC, CU, and LDEV numbers of the shredded volumes, and the number of times the system wrote dummy data to the volumes. For example, if a binary file is named 00-01-11-03.bin, the LDKC number is 00, the CU number is 01, and the LDEV number is 11. The filename also indicates that the system wrote dummy data to that volume three times. A binary file contains the first 512 bytes of data of a shredded volume (LDEV).

  • The file name of a text file appears as follows:

    shred_finish-time-of-shredding-operation.txt

The compressed file is saved with the time zone setting of the SVP. If the compressed file is decompressed on the computer, the time stamp of the decompressed file appears with the time zone setting of the computer. The time stamp of the decompressed file might be different from the actual finish time of the shredding operation.

In the text file, you can check whether the shredding operation ended normally. The following shows example contents of the text file:

DKC S/N: 90406
Day/Time started: 2019/02/21,10:04:09
Day/Time ended: 2019/02/21,10:05:11
WR Data Pattern: 0x00-0xFF-0x00
Result: Normal (No data assigned-No data assigned-No data assigned)
LDEVs:
0x00:0x40:0x01
0x00:0x50:0x01
0x00:0x60:0x01
0x00:0x80:0x01
0x00:0x90:0x01
0x00:0xA0:0x01
0x00:0xF0:0x01
0x00:0xFE:0x01
0x00:0xFE:0xF1
How to check shredding results

Check the status output after “Result:” and before the parentheses. If the shredding operation normally ended, “Normal” is output. If the shredding operation failed, “Failed” is output. When “Failed” is output, retry the shredding operation. If the shredding operation still fails, contact customer support.

Each of the statuses in the parentheses after "Result:" indicates the termination status of each system operation that wrote dummy data to the volumes. In the preceding example, the system wrote dummy data to the volumes three times. The following table lists and describes individual statuses.

Termination status in the parenthesesDescription

Normal

The shredding operation normally ended.

No data assigned

The shredding operation was executed on an unused DP-VOL.

In this case, the system did not write dummy data on unused DP-VOLs. However, if the volumes to be shredded included the following volumes, the system wrote dummy data to these volumes:

  • DP-VOLs being used
  • Regular internal volumes
  • External volumes

Not executed

The shredding operation was not executed with the specified parameters.

Canceled

The shredding operation was interrupted.

Failed

The shredding operation abnormally ended.

Data verify error

An abnormality was found while the file containing shredding results was being verified.

Data transfer error

Outputting shredding results to a file failed.

Parent Topic

Canceling shredding
Parent Topic
Child Topics

Stopping a shredding operation from HDvM - SN Tasks window

You can stop the volume shredding process.

CautionIf you stop the shredding process, you cannot restart the process. Data integrity of the volume is not guaranteed.

For VSP E series: You can interrupt the shredding process by using one of following:

  • Tasks window
  • The menu in Interrupt Shredding Task window.
For a faster response, use the Tasks window to stop the shredding operation.
TipFor VSP E series: The shredding tasks cannot be interrupted if either of the following two conditions exist:
  • Status of the shredding task is Failed.
  • Format/Shredding Task Status is Shredding on the Parity Groups window or Logical Devices window.

In this case, perform the interrupt operation from Interrupt Shredding Task window.

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. In the Storage Systems tree, select Tasks.

  2. Click the task name of the desired task in the Task Name column.

    The Task Properties window opens.

  3. Click Abort in the Shredding Data pattern field.

  4. Verify the displayed settings and click Yes.

    The shredding process stops.

  5. Click Close in the Task Properties window.

Parent Topic

Stopping a shredding operation from HDvM - SN Interrupt Shredding Task window

You can stop the volume shredding process from the Interrupt Shredding Task window.

CautionIf you stop the shredding process, you cannot restart the process. Data integrity of the volume is not guaranteed.
NoteWe recommend to use the Tasks window to stop the shredding operation if you want faster response.

Before you begin

You must have the Storage Administrator (Provisioning) role to perform this task.

Procedure

  1. Open the Interrupt Shredding Task window by any of the following ways:

    • Using the Logical Devices window

      Perform either of the following operations:

      • In the Storage Systems tree, select Logical Devices to display the LDEVs tab. Then, click More Actions > Interrupt LDEV Task > Interrupt Shredding Task.
      • On the Actions menu, click Logical Device > Interrupt Shredding Task.

    • Using the Parity Groups window

      Perform either of the following operations:

      • In the Storage Systems tree, select Parity Groups to display the Parity Groups tab. Then, click More Actions > Interrupt Shredding Task.
      • On the Actions menu, click Logical Device > Interrupt Shredding Task.

  2. Verify the displayed settings, and then click Apply.

    The shredding process stops.
    NoteIf the shredding operation being performed is interrupted, the end times of following tasks in the Tasks window differ:
    • End time of the shredding task being performed.
    • End time of the task for the interruption of shredding.

      The time difference above is approximately 10 minutes.

      To determine whether the shredding task is finished or not, confirm the status of the task. If Status is Completed or Failed, the shredding task is finished.

Parent Topic