Full Write

The Full Write function writes the entire cartridge with a specified block size either with compressible or incompressible data and output performance data.

  1. The Full Write function erases data on the cartridge that is used for the test.
  2. The Full Write function takes approximately 2 hours when incompressible data is written, less time for compressible data.
  3. The Full Write function runs only on tape drives, not on autoloaders or libraries.
The Full Write test can be used to
  • Demonstrate that the drive can write the full amount of data on a cartridge.
  • Reveal system performance bottlenecks.

    Full Write runs the test with incompressible data first, then runs the test with compressible data. If no difference in overall performance is observed, a bandwidth limitation might be caused by the system or cabling or HBA.

  • Identify system issues with compression.

    Compression is always turned on during the full write. When run with compressible data, the output shows the compression rate. If it is higher than 1.0 but your system is not able to compress data on the cartridge, check your device driver and software settings to see whether they disable compression.

To run a full write on tape drives within a library, the library must be in online mode.

  1. After the device you want to write to is selected, start the Full Write function by selecting Test > Full Write from the actions toolbar.
  2. Click OK to start the full write.
  3. ITDT-GE then shows the Full Write screen. If no cartridge is inserted, ITDT-GE prompts you to insert a cartridge. Either insert a cartridge and click OK or stop by clicking Abort.
    Note: If ITDT-GE detects data on the cartridge, it shows the following message.
    Figure 1. Overwrite data?
    Overwrite data?

    Click Yes to continue the test if you are sure that data on the cartridge can be overwritten. If you are unsure, click No to stop the test.

  4. The system prompts for entry of a transfer size between 16 KB and the maximum block size that is supported by the system. Maximum value is 512 KB. Select the appropriate value for your system.
    Figure 2. Transfer size
    Transfer size
  5. Select the type of data to write, either [C] Compressible or [I] Incompressible.
    The full write can be stopped by clicking Abort.
    Note: It can take some time until the full write actually stops.

    "Compressible = Yes" means that the data written was just zeros so that the data can be compressed by the drive with a maximum compression ratio. "Compressible = No" means that a data pattern was written that the drive almost cannot compress at all. If the compression ratio is 1, the drive was not able to compress the data (equivalent to 1:1 compression ratio). If the compression ratio is 94.0, the drive was able to do 94:1 compression. It means that 94 bytes in the original data was compressed to 1 byte on the medium. 100.0 means 100 bytes is compressed down to 1 byte on the medium.

    If all write operations are finished, ITDT-GE shows the performance statistics for the selected block size that is written on the cartridge, in the Status Information area. If an error occurred during the full write, data is only partially written.