Enabling and disabling logical block protection

You can specify logical block protection for read and write operations, or only for write operations. You can also disable logical block protection. By default, logical block protection is disabled because of performance effects that result from cyclic redundancy check (CRC) validation on the server and the tape drive.

About this task

Read/write operations to empty or filling volumes depend on whether the volumes have logical block protection. Protected and unprotected data blocks cannot be mixed on the same volume. If you change the setting for logical block protection, the change applies only to empty volumes. Filling and full volumes maintain their status of logical block protection until they are empty and ready to be refilled. For example, if you disable logical block protection and the server selects a volume that is associated with a device class that has logical block protection, the server continues writing protected data to the volume.
Restriction: Logical block protection is available only for certain device types. For more information, see Drives that support logical block protection.

Procedure

  1. To enable logical block protection for the 3592, LTO, and ECARTRIDGE device types, issue the DEFINE DEVCLASS or the UPDATE DEVCLASS command and specify the LBPROTECT parameter.
    For example, to specify logical block protection during read and write operations for a 3592 device class that is named 3592_lbprotect, issue the following command:
    define devclass 3592_lbprotect library=3594 lbprotect=readwrite
    Tips:
    • If you update the value of the LBPROTECT parameter from NO to READWRITE or WRITEONLY and the server selects a filling volume without logical block protection for write operations, the server issues a message each time the volume is mounted. The message indicates that data is written to the volume without logical block protection. To prevent this message from displaying or to have IBM Spectrum® Protect write data only with logical block protection, update the access of filling volumes without logical block protection to read-only.
    • To improve performance, do not specify the CRCDATA parameter on the DEFINE STGPOOL or UPDATE STGPOOL command.
    • When data is validated during read operations by both the drive and by the IBM Spectrum Protect server, it can slow server performance during restore and retrieve operations. To reduce the time that is required for restore and retrieve operations, change the setting of the LBPROTECT parameter from READWRITE to WRITEONLY. After data is restored or retrieved, you can reset the LBPROTECT parameter to READWRITE.
  2. To disable logical block protection, issue the DEFINE DEVCLASS or the UPDATE DEVCLASS command and specify the LBPROTECT=NO parameter.
    Restriction: If logical block protection is disabled, the server does not write to an empty tape with logical block protection. However, if a filling volume with logical block protection is selected, the server continues to write to the volume with logical block protection. To prevent the server from writing to tapes with logical block protection, change the access of filling volumes with logical block protection to read-only. When data is read, the CRC results are not checked by the drive or server.

    If a disaster occurs and the disaster recovery site does not have drives that support logical block protection, you must specify the LBPROTECT=NO parameter. If the tape drives are used for write operations, you must change the volume access for volumes with protected data to read-only to prevent the server from using the volumes.

    If the server must enable logical block protection, the server issues an error message that indicates that the drive does not support logical block protection.

What to do next

To determine whether a volume has logical block protection, issue the QUERY VOLUME command and review the value in the Logical Block Protection field.