VSP DRR Processors Test

A Data Recovery and Reconstruction Processor (DRR) is a microprocessor (located on the DKAs and channel adapters) that is used to generate parity data for RAID-5 or RAID-6 parity groups. The DRR uses the formula “old data + new data + old parity” to generate new parity.

This test monitors the usage of each DRR processor on the storage device, and reveals the over-utilized processors (if any).

Target of the test : A Hitachi VSP storage device

Agent deploying the test : A remote agent

Outputs of the test : One set of results for every disk processor on the target Hitachi VSP device being monitored

Configurable parameters for the test
  1. TEST PERIOD - How often should the test be executed
  2. HOST - The host for which the test is to be configured.
  3. PORT - The port at which the device listens. By default, this is set to NULL.
  4. USERID and PASSWORD – To extract metrics from the target storage device, the eG agent should be configured with the credentials of a special user account, which is specifically created for use with the Java export utility. This user account should fulfill the following conditions:

    • Should not possess the ‘write’ permission;
    • Can be of any user type; however, to ensure that the eG agent collects statistics pertaining to all storage partitions, it is recommended that this user is of type storage administrator;

    Specify the credentials of such a user in the USERID and PASSWORD text boxes.

  5. CONFIRM PASSWORD - Confirm the password by retyping it here.
  6. TIMEOUT - Specify the duration (in seconds) within which the SNMP query executed by this test should time out in the TIMEOUT text box. The default is 3 seconds.
Measures made by the test:
Measurement Description Measurement Unit Interpretation

DRR processor usage

Indicates the percentage of time for which this DRR processor was in use.


A high value or a value close to 100% is indicative of a high write penalty condition. In such a case, you are advised to consult with your Hitachi Data Systems representative for for further information.

By comparing the value of this measure across processors, you can accurately detect imbalances in load distribution, and rapidly identify the affected DRR processors. To ensure that load is balanced within the subsystem, you might want to consider relocating volumes using Volume Migration.